Well, you're right, I didn't realize that you were replacing the processor, reading comprehension isn't what it used to be.
In general, if I were paying for a new processor, I'd get a new fan just for the service life. As to what fan, I don't have an opinion on that. I recently picked up a couple of 2.4gig P4 chips for an upgrade, I bought the Intel retail package for $12 more, comes with a fan that Intel blesses for that particular processor. Seemed like a good idea at the time.