The big brother big sister program is really nice and I still stay in touch with my big and little even though I am now a third year. The bigs are good for asking questions about classes, getting "oldies", finding out whether or not you should buy a book for a class. The big brothers and sisters are usually matched in some way such as another student from your same undergraduate or maybe the same state.
I am sorry that I don't know a lot about what happens when you fail a class. I am sure that there is a way to make it up if it is just 1 or 2 but I'm not positive about the protocol. I would tell you not to sweat it though. Dental school is hard but everyone seems to pass. We are all good students so it isn't much of a problem. I know at the end of our first year there were a very few students (2 or 3) who repeated first year. We had only 1 drop out because she decided that she didn't want to be a dentist.
Pretty much no matter where you live in the 'burgh you will have plenty of good restaurants. One of the best parts about these neighborhoods (Squirrel Hill, Shadyside, and Oakland) is the amount of great restaurants. Some of the best ones though aren't chains (even though there are a lot of chains) but individual one of a kind restuarants. Oakland has a couple amazing ones including 1. Lulu's noodles/Yum Wok, 2. Indian Garden, 3. Fuel and Fuddle, 4. Mad Mex, 5. Sushi Boat. Another great thing is that several of these places have half off specials at certain times (happy hour and late night) or with student IDs.
I hope that I answered your questions and please post again with any additional ones that you might have. Don't worry too much about failing classes, I think it is a pretty rare occurence and there must be a system worked out for those who do.