There's another thread around here where a member goes to great length to remove a heatsink from a CPU. I believe it was one of the older models, which used an actual adhesive pad, gluing the sink to the CPU.
If yours is like that, be prepared to fight with it (gently) -- let us know if yours is like this..
OTOH, if your machine is half-ways modern, and has a decent CPU in it, and real paste in between, it should be easy as pie, literally, to separate the two surfaces. There's no real "bond" formed by heat transfer paste; it's intention is just to fill in tiny imperfections & scratches in each surface, to provide a uniform heat-transfering contact between the two items. It is not glue (usually).
PS - Silicone
, not silicon