If you bought a 2-year PRP through Gamestop, and it has not been fully two years yet, just take the console (and what came with it in the box) to any Gamestop, preferably with your receipt that has the 2-year PRP on it. If you lost the receipt, they can look it up by the serial number.

So long as you didn't open up your system to repair it yourself or anything, you should be JUST FINE. If anyone gives you any hassle, ask to talk to the Store Manager. In the unlikely event that the SM fails to adhere to the return policy, tell them that you need the phone number to their District Manager, and don't take no for an answer. Though again, that's only if they're not holding up their end of the 2-year PRP.

Hope it works out for you.