I am using a borrowed PowerBook G4 and the person included one of those USB powered fan stands. Didn't know why until I figured out the internal fans weren't working. So I came to ifixit to get the instructions and parts to replace the fan.
Success! The installation was fairly straightforward, if you follow the instructions. Took about 30 minutes.
The best way to keep track of the screws, I used a plastic ice cube tray and put little numbered stickers on each cube. I put the screws from Step 1 in the cube marked 1, screws from Step2 in cube 2.....
Then reversed the process to reassemble, no left over screws!