Make sure you:
use thermal compound between the heatsink & chip surface

ground yourself before handling any delicate parts.

be careful when locking the clips for the heatsink.

It's not really difficult --just requires care and good light.
If one of your PCI cards or a case-fan is blocking clear access... move it-- it's worth some minor inconvenience to be sure everythings seated and locked-in properly the first time.
Also a good time to clear any dust/debris out-- when you have full access.