With care

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Do you need to remove the HSF, or is that already done? To take it off undo the mounting while the proc is hot, and gently apply a twisting motion to loosen the grip of the thermal interface material. Once it loosens you should be abe to twist and lift gently and have it come off.
To get the proc out you have to release the socket clamp. There should be a metal lever lying along one side of the socket. Gently swing it up and back to release the grip on the pins. The processor should lift right out. Be careful of the pins. I suggest you have the original piece of foam from the packing case, or another suitable piece of medium density foam (the kind that most add-on boards ship with works well), and set the processor pins-down onto the foam. You can then use a little alchohol to clean the remaining thermal crap off the heat spreader.
Good luck.