Fan stopped spinning up when CPU heat rose, so I replaced it
CPU temperatures had started to spike on my laptop (80C or higher) while doing mundane things at low percentages of CPU, and fan didn't spin up to cool the machine. Apple did diagnostics, said all was well. Temperature Gauge Pro detected a problem with fan, however, so I ordered a replacement to see if that would fix the problem.
Great. Took about 20 minutes, fan works, temperature profile back to normal, laptop is happy again.
You should use a #000 Phillips screwdriver, not #00. The screws are easy to strip, and #000 fits better, makes it easier to get tight screws loosened without stripping screws. And, if you stripped a screw with #00, you still might be able to get it out with #000. Also, make sure to pay attention to the shape of the 7 smaller screws in the bottom of the laptop. 4 of them have a larger diameter neck above the threads. Those go in the four holes along the bottom of the case (the edge opposite the hinge, where you open the laptop).