My Rev A MacBook was in fine shape until the fan started to get noisy and work half the time. The laptop would over heat and have performance issues. Not to mention sound like a lawn mower when the fan decides to work.
Ordered a new fan from ifixit which came in the mail within 2 weeks. Followed the easy guides and now my 2006 MacBook is as good as new.
Make sure you have a can of compressed air ready to blow out the gross dust bunnies you will encounter replacing an old fan. I cleaned out the entire logic board which was unfortunately caked with my body hair. :S