Replacing Fan Inside hard drive...possible?

Huh?
Eazyduzit you seem lost (no offense) so find yourself a good A+ tech until your knowledge catches up with your hardware.
You are learning, which is good (teach & learn :^) but we can help you only so much...
If your drive is pooched, it's pooched (replace it).
Hope you got your data off first... you've got a DVD burner, right?
Concentrate on keeping your newer/faster/better HD alive, by attending to your case cooling if required.
Good luck!
L8R