You have 2 options here. Get a slim, or fix your rrod the right way. New thermal paste alone does nothing, to fix it right you would need to get rid of the x clamps and replace with screws and washers, new thermal paste, and reflow the board around the CPU and gpu. There's guides all over the Internet on how to do it, but honestly if it's in your budget get a slim. Better hardware, built in wifi, etc.