Please Advise!

Yes you can do it, but why? You will spend all of your time on trains with no time to experience all these beautiful places.

You can get the schedules by using by using the Deutsche Bahn journey planner. They have all the schedules for Europe.
http://reiseauskunft.bahn.de/bin/query.exe/en

Do you really mean to do these journeys on three consecutive days? Or are your travels days 1, 2, and 3 separated by 2-5 days to enjoy these wonderful places you will visit?

I know, I boxed myself in and didn't plan well. New at this. With reservations, etc., my only other choice is to cancel Murren altogether and go from Lucerne to Colmar. Just hate to miss that little hamlet.

"Just hate to miss that little hamlet."

The point of going to Mürren isn't to see Mürren; it's a village of 400 people, and almost every square inch is covered by a structure (chalet, hotel, etc). The point is to be in the Berner Oberland, an astonishingly beautiful place, and have time to walk, or hike, or take lifts, to see the mountains, waterfalls, valley, etc. And it's very weather-dependent; you want several days there to really see it properly.

So, with your schedule, don't even attempt to detour to Mürren. Instead, spend two nights in Luzern. It's a very pretty small city, and you can then go to Mt. Rigi or Mt. Pilatus as a day trip from there (these won't take a full day). Or, skip Switzerland entirely, and plan a separate trip there at a later time. You can't see everything on one trip; instead of trying to do that and being miserable, use your time to enjoy the places that you do see on this trip, and as Rick says, "assume you will return."

Yes, you can get train schedules for almost all European trains on Bahn (German Rail) http://reiseauskunft.bahn.de/bin/query.exe/en, by following Rick's tutorial: http://www.ricksteves.com/travel-tips/transportation/trains/online-schedules. This will only have prices for trains that start or end in Germany, but it will tell you which trains have mandatory reservations. Assume international trains will be cheaper bought in advance as non-refundable and non-exchangeable tickets. Domestic trains within Switzerland don't need (or allow) reservations, and prices don't change, so you can buy on the day of travel.

To buy trains leaving from Austria, use http://www.oebb.at/en/. For Switzerland, use https://www.sbb.ch/en/home.html. And for France, use http://www.sncf.com/en/passengers (on the left, choose Reservations).

This is what happens when Rick mKes places like Mürren and Hallstatt sound so irresistible that people include them in an itinerary without checking on travel times to link them. In your case it is Hallstatt that is the real problem---9+ hours by train to get to Luzern from there.

But I know the feeling---I get that "I have to go there!" feeling whenever I see a photo of Hallstatt. We will be in Vienna for a week in September, coming from Slovenia, and I tried and tried to make Hallstatt fit into our schedule, but failed.

Where else are you going on this trip? Is it possible you could rearrange to put Hallstatt in a different place in the itinerary to make it more practical? Of course you may not be able to change your reservation there, so this suggestion may be impractical.

I agree with Harold that you should omit Mürren. Not because the travel times are so bad---it is less than 3 hours from Luzern, and only 4 tomget to Colmar---but because it is not really worth going if you only have one night to spend there.

Or omit Hallstatt and add time to Mürren.

For what it is worth, I lived in Austria for 9 years before I went to Hallstatt. It is beautiful, yes, but I have seen more beautiful places. I guess some people just need to get "that picture."

I've been studying train schedules (when I can get them) and remain pretty much confused. . . . do I need train reservations/tickets in advance?

Susan, sounds like you need some basic beginners info for where to look for train info.
I don't know where you have been looking for train times, but, as Sam said, the best palce to look for train times for most of the rail companies in Europe is on the DB (German Railways) site: https://www.bahn.com/en/view/index.shtml
They will however only sell you tickets (and only give prices) for trips within, to or from Germany. For prices you need to look on the website of the company running the train.

Long distance trains in Austria and France (but not in Switzerland) have discounts if you buy in advance. If you buy normal tickets they automatically include reservations if needed.

For your education on trains, read this website: https://www.seat61.com/
Especially these three pages: https://www.seat61.com/international-trains/trains-from-Vienna.htm#Vienna-Austria
https://www.seat61.com/Swiss-trains.htm
https://www.seat61.com/France-trains.htm

Day one: Hallstatt to Lucerne; Day two: Lucerne to Murren: Day three: Murren to Colmar.

Neither Hallstatt nor Colmar have an airport, so there must be at least one trip before that (XXX airport to Halstatt), and another Colmar to YYY airport.
DO NOT travel on 3 consecutive days. 2 nights should be a minimum in any place, and you really need 3 or 4 nights to appreciate what you have travelled all this way to see, not just tick it off a list.

Is Hallstatt changeable? I was there last week and after driving over 3 hours to the town (and 3 hours back) I got on the next boat over the lake and left after less than one hour.

Why, I hear you shouting??? Because I had visited Bad Tolz the day before and loved it as a delightful town and seen several more beautiful villages as I drove through the Salzkammergut and was totally unimpressed with Hallstatt. Think Rothenburg ob der Tauber on a really busy day and at least double or triple the density. In my opinion what had once been a beautiful village became nothing more than a completely overwhelmed tourist trap with locals who, while collecting all the money from people from all around the world (but mostly a very large country whose residents speak Chinese), can't stand the influx and are particularly unhelpful.

It was the only town or village in the Tirol or Salzkammergut with no flowers. No window boxes, no flowers along the road, no flowers in the roundabouts. None.

Exact change (one euro) to pass the turnstile into the toilets, a complete flood of tourists into the church who made NO effort to lower their voices as I was attempting to say prayers, more selfie sticks than i have seen in Florence, Rome and Venice combined, and an absolute scrum to walk down any of the streets, except only a hundred or so who went up the side streets to the waterfall.

Such a pity, but there I was, getting on the next boat. By the way, why the boat when I drove? This was mid-week (intentionally) and the queue to go into the full number 1 carpark was around the corner, the number 2 carpark has been closed, the number 3 carpark was nearly full and nearly 3 miles back to town was too far for my old legs to go on spec as when you arrive you can't see the town from the road because it has been put into a tunnel behind the town. So I drove all the way to the end of the lake, parked one town away from the Hallstatt train station, took the train 6 minutes and then the (very very full) boat which dropped me in the centre of town.

Anyway, back to your question - Hallstatt is the really remote location of your stops.

Is there anything you can do to change or cancel any of the trip - you really do have way too much wedged in there, as you have discovered.

How can we help?

Many, many thanks to all who responded! Your info has been extremely helpful and especially grateful for the train website and info. We decided to cancel Hallstatt, spend an extra night in Lucerne and feel much more comfortable. Thanks again!!

Good choice.

After reading Nigel's post I am glad I did not strain our own itinerary with a visit to Hallstatt!

Hey Nigel,

Maybe it's gotten worse in Hallstatt. We went 9 years ago on a weekday in mid October. Barely a soul in the village. Still, after 2 hours we were bored. Too many other cute, scenic villages to visit in Austria.