I am putting this out there, since it worked for me.
Apple refuses to warranty this machine, since I changed the battery/hard drive on the machine as a user replaceable part.
So If you have a video card issue, no need to put it in foil/oven/hot air gun or blankets to heat it up. I have a simpler solution!
Open up back cover and disconnect the 2 fans. Put the lid back, then turn it on and let it get to the bad video screen. Leave it on for a good 7-10 min and let it get hot. This will automatically solder reflow the chip without pulling it all apart and doing oven techniques.
I did a hair dryer reflow once and it worked, so I wondered why not let it heat up on its own without fans, the heat stays in and it has the same affect. This procedure makes it work for about 1 month. Then you need to do this again. Disconnecting fans is easy and can be done repeatedly. I don't even screw in my back cover anymore!