If you book all the way to Sunderland (not St Peter's!) your train ticket
costs the same as to the Toon provided you use the Metro. If you catch the train
over then it's an extra 2 quid each way.
If you're travelling direct from Newcastle then best way to get over is to give the official buses a wide berth and catch the Metro. There will probably be special services running direct to St Peter's. However, I personally would just get a normal service over and get off at the Stadium of Light. That way you should have a more civilised journey to the ground at the other end. The journey time is about 25 minutes. The service isn't very frequent though.
Surprisingly, there are apparently a few decent pubs in Sunderland, although none of them are particularly near to the ground. They're all shown on the pub map below. It goes without saying that no pub in Sunderland will be welcoming when we play there.
Football Ground Guide
A Love Supreme (decent unofficial site)
Ready To Go (ditto)