Can't remove CPU heatsink because two of the screw heads are damaged

I replaced the thermal paste on the CPU and Radeon chip in a 4320s a couple years ago due to over heating causing shutdown on boot which fixed the issue.

It's happening again but this time I can't remove the heat sink because two of the screws holding it in place are damaged and won't turn no matter what screwdriver I try. The driver just spins in the head of the screw.

Any advice would be greatly appreciated.

Thanks in advance!