Gently cut the epoxy all the way around.....Then get acookie pan and heat it up on a stove burner say 350 to 400 should do it...

Put on lots of thermal paste on IHS and then holding sides of the PCB with Long Plyers/BarBq Prongs work too IHS DOWN set it to the Pan...The IHS should fall off in about two/three seconds...make shure yo pull it straight up and then turn upright so heat can rise away from core....Clean up excess solder with razor very carefully...

Note: do not spill Beer on hot chip or use breath to blow on hot chip ..Whereass you can crack the Core....dOnT AsK