10 - 30 分钟
The old fan had worn out bearings which caused lots of noise and bad performance.
The switch went well. Took about 30 minutes because the screws were stripped. The comments were very helpful.
If the screws are stripped, take a similar size flat screwdriver and put at 45 degrees into the screw so the screwdrivers corner points into he screw, and give a slight tap from each four directions. Then take your Philips screwdriver and try to unscrew. This made it very easy for me.