Advice Re Precision T3600 CPU Upgrade

Hi All

My system is running a Xeon Quad Core E5 1620 @ 3.6ghz.

I understand I can install an Eight Core E5 2665 2.4ghz for a good speed boost, and they are available quite cheaply it seems.

My BIOS is A18.  PSU is 425W.

Is it a fairly easy straight swap to do this?  I can see there is already a MASSIVE cooling device on top of the CPU, which looks like a giant Heatsink.  I am hoping that would do the job for the faster CPU, and assume I would need a bit of heatsink compound when fitting it back onto the new CPU?

Any advice appreciated