My early 2008 MBP's graphic card and attached mother board went a few months ago.
I contacted Apple and discovered that Apple had a free replacement policy that ran for four years, ending
Dec 31, 2012 since those cards were apparently faulty. Apple said that even though the date for free replacement
had expired, if I brought the machine to an approved Certified Apple Repair Center, and received a diagnosis
that the card was the problem, they would make an exception and replace the card at their cost. I did as they suggested, and indeed they replaced the card at their cost six-months past the posted deadline. So before you go ahead and pay $300-400 for a new used board I'd check with Apple technical support. I found them surprisingly helpful and flexible. And realized why I own 3 Macs.