The CPU one got a printing with CELL BE on its IHS and that's the thing you want to deal with overheating problem not the RSX as I mentioned earlier.
And I see, so the IHS got poped out when you removed the heatsink right? probably its a good time to reball the RSX, reflowing the motherboard requires more things, one is you need to flux the rsx chip and other things. Or buy a new one since you got a overheating problem (unless you know someone who can do IHS removal and reball the GPU at the same time)
although I did reball my PS3 by myself (since I got a IR Rework machine anyway) and do a overhaul thing on it remove the IHS and reapply some high quality thermal paste on it, and now my PS3 is running fine.