iMac 2009 to 2011 (A1311/A1312) Upgrade Guide – MacintoshMen
2010 iMac GPU and CPU upgrade, is it worth it? - YouTube
Amazon.com: Original 1GB Graphics Card for Apple iMac 2010 27" Core i7 2.93 Desktop Computer MC784LL/A MC784 A1312, ATI Radeon HD 5750 GDDR5 1 GB Video Cards GPU Upgrade Replacement Parts : Electronics