I've been to ND maybe a dozen times over the years and for 4-5 Pitt/ND games. It's one of the best and most unique college football environments in the country. My advice especially for some guys going down for the first time is to spend most of your pre-game time on campus. Tailgating at ND is about like it is anywhere else but the on-campus gameday environment is unique and is really what it's all about. Get there early and walk around , check out all the landmarks like the grotto, the golden dome, touchdown Jesus, etc. There are student organizations and groups all over the place selling food, some of which is really good--like the steak sandwiches. The bagpipers fire up at the golden dome at about 10:30, the Irish Guard and cheerleaders are there. There is a big "fanfest" football-oriented carnival with live music, former D players, etc. that goes on at the track facility. The team walks the central campus quad to the stadium a couple hours before the game and that's worth seeing. Lot of good cool stuff to see and do, and I think you'll find the ND faithful to be gracious and welcoming, it's a real point of pride there.
As far as bars it's pretty limited. Legends is in the parking lot just south of the stadium, the Linebacker Lounge is a legendary ND dive bar, there are beer/cocktail tents on campus with big screen TVs etc. South Bend itself is a dump and the ND campus is like an oasis in the middle of the desert.
It's a great college football environment and I've seen a few lifelong ND haters become converts after visiting the campus for a home game. Get there early, soak it all in, and have a great time.