I just did exactly that for a customer (technically it was a 23 blade 2.15A fan) it works great, the fan connector leads are just barely long enough to fit in the channel in a CFI-1215A model though, so careful not to tug too hard after plugging the fan connector and seating the fan in place.

These screws are T9 security, or, if they are designed to be T8 security, they also accommodate T9 bits and you should definitely use T9. Source: Myself after stripping a highly torqued bolt 🤦‍♂️

Pliers are a bit too much in my opinion, a bit too easy to strip something essential or gouge the metal, and there is Loctite involved from the factory here also. I'd recommend using the long thumbstick extender locked onto the stick, since it has the rubber grip tip and is longer it should give you enough torque to get the threads unstuck and unscrew the thumbsticks. Use a slight downward force as you turn the stick to make sure the grooves don't strip on either the extender or the stick piece. At least try this first before moving to pliers.

You just need the proper driver bit (I believe it is a Torx 5/T5 ?) first, follow steps 1-4 to remove the bottom cover, then the set screw is at the lower portion of the unibody frame smack dab in the bottom middle of the trackpad edge. To “tighten” the click (if click is not occurring or too “loose”), turn the set screw 1/8th turn in a clockwise direction. Then test the click t see if it improves, if not go 1/8th turn at a time. If you turn it too much or turn counter-clockwise too much it will release from its mount hole and they are REALLY annoying to try to re-thread.

Recommend being very careful on this step and the following step when using any opening tool to always keep the “pointy end” up when prying, especially about 40mm up the side, to avoid completely destroying the speaker diaphragms.