Did the same thing myself - I killed my processor separating it from the heatsink.
Try the two p's - patience and prayer.
After my experience I would say the best bet is to get hold of a one sided razor blade, or similar, and gently slice the two apart.
The odd thing was that when I attempted it - I used everything from a jack hammer to a scalpel - the cpu stuck like it was super glued, until it started to give at which point the two parted company so quickly that the cpu flew one way and the heatsink the other. I picked my cpu up about four feet from where it started.
My point is that there does not seem to be much holding the two together, it is a matter of finding the weak point. Use something which is wider than the cpu, if possible, and work it between them round the edges. I marked my heatsink using the scalpel.
Best of luck - go gently!