Originally posted by: Zap
1) Don't lose any of the little screws or heat pads on the components in case you ever have to revert back to air cooling.
2) Take your time.
3) Remember all the parts that the stock heatsink cools, and make sure all those parts continue to be cooled. If using a full-coverage block, make sure you have thermal compound or a thermal pad in all those areas. If using a GPU-only block, make sure you use heatsinks on those components, perhaps with a fan blowing onto them.
4) When removing the stock heatsink, the large area of the GPU will cause it to stick to the heatsink from suction. You may have to use a twisting motion to separate the two. Alternately you can use a slotted screwdriver as a lever between the two. There is a metal ridge around the GPU. If you get the screwdriver between it and the heatsink, a simple twist will break the suction. Just be careful that you are on that metal part and not some component or the bare PCB.