Tickets were easy--think I got them from ACE Tickets (A local Boston ticket broker) I sat in the BC section at about the 40 yard line, and I recall paying about 50% over face value. I probably could have done better buying before the game. Regardless, there is a healthy secondary market. ACE is pretty reputable, I've used then for Red Sox tickets a couple of times also.
I took the "Green Line" (subway) to the game to avoid the traffic/parking. Worked well going to the game, but the line to get out afterward was rather long.
The stadium isn't very impressive--kind of reminds me of a high school stadium, only bigger.
It's in Boston--home of some of the rudest people in the country. I wouldn't be concerned about your physical safety, but there are a lot of "big mouths" around. (It is not like going to an Oakland Raiders game as a fan of the visiting team.) I would guess the stadium will be at least a third ND fans. The 2012 game was also a night game, so there was plenty of time for the BC faithful to be well lubricated.
Boston can be a nice place to visit--I lived there for two years, and I can safely say I wouldn't want to live there.
I also went to the Shamrock series game at Fenway. Sight lines were horrible for football.