Lourdes

I was there in May 2013 before the flooding. The Pyrenees are beautiful, but it's an area largely ignored in guidebooks. Try Lonely Planet or websites for the region.

We were only there for a day as part of a hiking trip so I cannot offer hotel advice, but the grotto, main church and underground church are interesting. Beautiful mosaics in the main basilica. In addition to the religious site, I highly recommend the Chateau Fort & Museum. I think it's one of the better-done folk history museums/historic forts in Europe. BTW, we visited on a rainy Wednesday off-season and there were very few people by the grotto. I'm sure in high season on a weekend it's a different story.

I'm Catholic, but to me Lourdes the town is ticky-tacky. BUT if you accept that it is what is, you can make it your own and find peace in the aspects of it that are important to you.

I took the TGV from Paris. Fine trip, but it's still six hours one-way. Recommend watching the Rudy Maxa episode on the Pyrenees. Doesn't cover Lourdes but is a good intro to the region.

Last time I stayed at Hotel Chapelle et Parc and was happy there. I'd suggest getting a room in back, away from the street. It's a simple, older hotel, but well-maintained. If it's not available, you could check booking.com, and I'd suggest getting something very close to the shrine. There is a lot of walking once you are within the shrine, so it's nice to be nearby.

I'd suggest taking a taxi from the train station to your hotel. It would be a long walk with luggage. It was an inexpensive taxi ride, probably less than €10, although the memory traces are little fuzzy.

Regarding how long to stay… I'd suggest checking the website of the shrine. I don't have the address, but it comes up on Google. That will give you an idea of the size of the domain, the number of places you can visit, and liturgical schedule. I had 1.5 days on my first visit, and I didn't feel that was long enough. When I went back I gave myself 4 days. But everyone's needs will be different.

A couple of suggestions.
--I found the very early morning Mass at the grotto to be very moving (and wonderfully quiet) although it may not be in English if that matters. Also if you decide to attend, ensure you identify the gate that's open all night. The main gate will be locked in the very early morning.
--Also, the high stations of the cross will take you up a mountain overlooking the grotto; it's really beautiful.

The website provides really good information. Also there is an information building once you enter the shrine.

Addendum to message above: I remembered that I had a hard time finding the actual website of the shrine, so I looked it up in my records. Here's the link:

http://en.lourdes-france.org/

One night and day should be enough time. If you take the TGV from Paris that gets to Lourdes at 14:30, then maybe you'd leave about the same time the next day to your next destination. See also How to Look Up Train Schedules Online.