Going to Berlin for an event and then will visit Auschwitz, Prague, Switzerland and the Black Forest, not necessarily in that order. Will probably rent a car to save some travel time. What maps do I need? Any idea what weather is like in early spring in Germany? I've got a couple more months to finalize plans but have already bought the event ticket and booked airfare. Please advise at your convenience. Thank you!
Will probably rent a car to save some travel time.
Care for IDP. In cities like Berlin rental cars are seldomly a plus. Use public transport - good to know.
Train connections recommended: https://int.bahn.de/en/
What maps do I need?
Most correct map for Europe: https://wego.here.com/
For best navigation without mobile connection: Sygic GPS Navigation: https://www.sygic.com/gps-navigation
Any idea what weather is like in early spring in Germany?
Full range possible from winter conditions with snow to nice sunny spring days up to 15°C.
I agree with Mark that it is not a good idea to have a car in Berlin. In fact, if you are going to the Black Forest, I would suggest taking a train down to that area. Overall, trains are a good way to go , so I would consider public transportation. However, if you decide not to, I would suggest checking Auto Europe for rental cars.
Gengenbach is a good place to consider as a base in the Black Forest, and it is one of my favorite places. I stayed in Gengenbach for 4 nights in 2022 and absolutely loved it. The town is very charming with beautiful half-timbered houses (it's frequently called a "chocolate box" village) and has a beautiful Altstadt, with quite a few restaurants and cafes to choose from. There are lots of things to do on a day trip there and it's very quick (and easy) 40 minute train ride from Strasbourg, if you wanted to take a quick day trip over to France. And if you stay in Gengenbach, one nice benefit is that you receive a KONUS card, which entitles you to free public transport throughout the Black Forest region. There are many charming villages in the region that you can visit along the Black Forest Railway, and there is also the Vogtsbauernhof (open-air museum) that is a joy to visit and easily accessible by train.
In terms of maps for driving, I just use Google Maps GPS. I've used it throughout Europe and the UK and have never had any real problems. I like it better than the satnav devices that come with cars, and most rental cars now have Car Play or the equivalent.
What do you mean by early spring? I was there in May and the weather was good, but in late March and early April you will undoubtedly get some rain and cooler weather. But it's all variable so you just never know.
I've convinced myself to get a Eurail Pass and travel by train and limit my choice of destinations a bit. I'll be in Berlin the first weekend of March and will come home the following Friday. From what you both have said, I can expect cooler weather at that time of the year, so now I know how to pack. I'll look into Gengenbach, as you suggested. It sounds right up my alley. I may take a trip into Switzerland, but I have no specific reason to do so, so I may keep that on the shelf for another trip. I've nixed the Auschwitz visit, partly because my time is limited and partly because I don't think I can take it right now. I'm taking this trip to pull myself out of a sad situation and I'm guessing a visit to Auschwitz just might tear me in two. Thank you both for your sound advice; I will take it all!!
and booked airfare.
Into Berlin I presume. Then where are you flying out of?  In Berlin the first weekend in March (6.7.8) and flying out the following Friday (13th). That does not leave much time. Just enough for a trip to Prague and back if you are really flying out of Berlin. If you do anymore than that, all you will be doing is riding trains and checking into and out of hotels. 
If you keep it simple, a Eurail Pass is overkill. You only need a train ticket to Prague and back to Berlin. 
I'll be in Berlin the first weekend of March
This is more late winter than early spring. Last 30 years climate data for Berlin. Local weather forecast for Berlin from regional public TV / radio broadcaster.
Book hotel early because ITB fair will end March 4 - appr. 100k attendees last year. Some stay longer.
I've got hotel in Berlin booked and looks like I'll just drop down to the Black Forest area and stay a few days there before I head back to Berlin airport. Had I thought about it more, I should have returned from Zurich or Austria; maybe I can make a flight change later. Trying to figure out my potential itinerary and just how much I want to do while there...I can plan for a more comprehensive trip another time. Thank you for the tips!
I use a Eurail Global Pass but then my travel style and trip durations are different from yours.
In your case I would suggest not getting the Eurail Pass simply because you are not over there long enough. Berlin to Switzerland can be done with a night train connection, haven't done that route myself but for me quite easy, a direct shot, multi-hour ride at night.
Going to Gengenbach is a 6 1/3 hour trip from Berlin Hbf, and you can get an advance Sparpreis ticket for around 68 EUR each way. When staying in Gengenbach, you will get a Konus Card which gives you free use of trains in the Black Forest region. So again, Eurail Pass is a waste.