Did you buy your mbp on a credit card? If so, they probably have a free extended warranty for you. Find out before you throw $350 at Applecare. My credit card is giving me one free year of extended warranty, so chances are, yours will too.
Sorry guys, I was on my iPhone and was being lazy...
Let me reiterate what I'm trying to say...
I HAVE an AppleCare for a MBP, unopened, but do not have a receipt. Will this be a problem, or what? Should I go ahead and open it up and register or whatever I have to do, or is some sort of purchase validation required?