Logic board replacement for mid-2010 macbook pro

I have a 15" mid-2010 macbook pro (i7 2.66GHz) that is one of many with a faulty graphics card. My computer started having panic attacks just after the logic board replacement program ended, yay for me. I took my computer in to an apple store where they confirmed the graphics card was causing the attacks. The options given to me were: buy a new computer ($1000's) or buy a new logic board ($600). In researching my problem I have noticed that it seems to be repeating itself both in models before and after my computer. I am somewhat hesitant to buy another mac now; one bad part seems to hold a big price tag due to design.

One employee told me to check sites like ebay for used logic boards because they sometimes sell for as low as $300. I have been looking at buying a logic board for a while and I can find them for between $300- $600. I'm just a bit scared to take the leap and purchase one. The rest of my computer works perfectly, but it has now gotten to the point where I just can't do much in photoshop, watch movies, or plug in a projector... all of which I bought my computer for. New computers I have been looking at (all PC) that will have the features I am looking for will be around $1000. A new mac would also be >$1000. I can't really afford to spend that much right now.

So, my question, does anyone have experience buying a used logic board from places such as ebay? Or other sites? If I can find one for <$600 I would buy it (unless I get a big *no* response here). If I can get this computer to last another 3 years or so, I will be able to afford a new one that will have everything I want. But, if I spend $600 only to have the computer crash again in a couple months, I will have waisted a lot of money. My only other option at this point would be to get a cheap PC, or keep putting up with panic attacks.

Any advice or comments is greatly appreciated!