iMac 2009 Logic Board

I recently had my 2009 21.5" iMac suddenly die on me while I was out of town. as there are no third party apple service providers in my area my first thought was to take the computer to geek squad. they soon informed me that they thought it was a shot logic board, but the technician didn't seem really confident. I have already bought a replacement iMac but I still have a number of uses for the old one if I can get it working. is there a way to know for sure it's my logic board at fault? if so, is there someone with a used 2009 iMac that they're getting rid of for other reasons?