fueldump,
If you purchase a new processor then it will come with a fan so no need to worry there. Two things I can think of that you will need to check. Does your new MB use the same spec memory as the old and does your psu (power supply unit) have the correct plugs. Older psu's don't have the processor plug that is now needed. A new one will cost £15-£20.
Regards
Stoney