Check this out.
Xtreme Systems forum user Fugger bought an Intel Mac mini core solo and upgraded it to a core duo on his own using an
Intel Yonah 2.16 Core Duo. He writes:
"Once the motherboard is out, flip it over and locate the plastic tabs that hold down the CPU bracket. Squeeze them and it will pop off. I highly suggest using one hand to hold heat sink level as it can and will flop to one side with possible damage to core edges. The same goes for reassembly. You will also see a small connector for a thermal diode attached to the underside of the heat sink once you have it loose, remove the clip if you want to remove it completely."
Pictures were up at the time of my sitting down to write this (11:30PM EST March 5), but have since disappeared. Hopefully he'll put them back up.