How do you fix a PS3?
Go to the link below and you can download a manual for $34/64 and fix it yourself. No special tools needed check it out
To fix the yellow light you can send it to sony to fix it for $150 and you will lose all your memory which isn't really recommended unless you are to lazy to take it apart. If you got to youtube and search up how to fix ylod on ps3 and there will be some videos that will show you how to take apart your ps3 step by step and what to do.
I don't think GameStop will fix your PS3. They are Places online the advertise PS3 repair and they also list many of the starting prices after you ship it to them. With Walmart's 2011 Black Friday price of $199.99 for a PS3 160GB with 2 games you might find it a better investment to just replace your old PS3 with a new console and full warranty.