Wow - I did exactly the same thing
Thx for sharing the details. I literally followed the exact same steps you did only to figure out I had the lights mixed up.
Shaky Mirror Fix 4th gen 4Runner
My side mirror was shaking a lot and the actual mirror housing seemed looser than it should be. There's a removable plate (just snaps on/off) on the bottom of the mirror housing and 3 Torx screws that hold the housing onto the support arm attached to the car...
