Sadly, the fix is likely temporary. The GameStop heating-and-cooling method sounds similar to the famous towel method that spread across the internet; remove everything (that’s easily removed) but the power supply from the Xbox 360, wrap it entirely in towels, plug the console in and let it run for 20 minutes, turn it off and unplug for 20 minutes, and it should work once again. The towel method often worked because it used the console’s own heat to re-melt solder on the GPU, but generally proved to be a temporary fix because of the inherent flaws in the motherboard that caused the problem in the first place.