Just so you know, the point of thermal paste is to transfer heat from the CPU to the heatsink. If you do need to replace the thermal paste, you only need like a small drop generally that when the heatsink is on top the cpu will be cover by a thin layer of it. If you put too much on it, you risk spilling onto the motherboard and causing permanent damage. I think you can also get some sort of thermal patch things (gray generally) that also do a job.

[note: I am from australia and am assuming that this sort of stuff is standard around the world]