your psu will work with your cpu at a higher speed, the only problem would be if you have increased the voltage alot, have a look in you bios and see if there are any voltage lines under what they should be, if there are, get a better psu.
for thermal grease, get artic silver III or Artic silver Aluminua.
i will leave the heatsink thing for other people, i cannot spell most of he names of them.