I know this has been asked before, but I honestly didn't have the time to look for it. My diamond membership is set to renew on October 1, 2012. How can I be sure it does not?

Sorry to become a basic member, but I can't really afford chess.com and ChessBase this year ;)

Sure, no problem! You can go to your account page at http://www.chess.com/home/account where you should find a link to cancel the auto-renewal basis of your subscription.