Upgrading the processor on a mid-2010 iMac | MacRumors Forums
Upgrade iMac Intel Core i3 CPU to Core i7 - iFixit Repair Guide
Amazon.com: Timetec 16GB KIT(2x8GB) Compatible for Apple DDR3 1333MHz PC3-10600 CL9 for Mac Book Pro (Early/Late 2011 13/15/17 inch), iMac(Mid 2010, Mid/Late 2011 21.5/27 inch), Mac Mini(Mid 2011) MAC RAM Upgrade :
Apple iMac 21.5" - Early 2010 Reviews, Pros and Cons | TechSpot
CPU upgrade for iMac 21,5" Mid 2010 | MacRumors Forums