I've only done Boston once, so there are others better qualified than me, but no one has answered yet.
A few answers/opinions: Regarding corrals, I suggest reading some on the race website. Basically, 20-30 min before the race, you should find your proper corral (which is based on your bib number)- don't worry, they will explain this to you at the expo. You do have a while prior to the race at the starting area, and I suggest leaving the school where they drop you off and wandering the streets around town a bit- lots of nice people will be out, sitting in lawn chairs, and some may even let you use their bathrooms. For the eating/drinking prerace- the best answer to this is to do some of you weekly long runs late-morning and find what works for you. You will probably want to eat a bit more in the morning.
As for what time to aim for, Sasha's calculator is very accurate:
http://asksasha.com/predictor.phpJust like any marathon, try to not go out too fast. Boston has some downhills at the start and you will have so much energy from the race that you need to really concentrate to not go out faster than you want. As for the hills- just train on some in SLC and you'll be fine, same as we would recommend for any race.
Good luck and have fun. Just remember- I think Boston is more of an experience than a race for most people. So have fun, enjoy it, soak in the atmosphere, and make memories.