Over time, our old Macbook's fan decided to slow down, then get noisy and eventually stop. When this happened, it would of course get beastly hot in a short time, and eventually crash.
Quotes were $400 to fix this problem. We fixed it with a little time and patience for $55 using the ifixit site parts and guidance.
A little over two hours, no problem. Works great!
Just get all your small tools, a magnifying glass, small magnet for pulling tiny screws (keep the magnet away from obvious critical areas,) and an egg carton to label the steps and associated screws in order. Be patient. Reverse, you'll be fine.