i can't find the original post i followed to disassemble mine, but here's how i did it. *use at your own risk*
with the truck off, press the bottom of the mirror all the way in with your thumbs so the top sticks out.
pry the mirror upwards and it should pop off.
i used a sturdy plastic putty knife and pried it up between the bottom of the mirror and the mirror housing.
i believe there are wires connected individually and directly to tabs on the back of the mirror.
take a picture so you remember how to reconnect.
i believe they are color coded too.
the mirror motor is what the mirror attaches to, and there will be 4 tor-x (or whatever the star shaped head is called) screws holding it in, and it has a round housing with many circular holes in it.
once the motor is unscrewed, disconnect the harness connected to the motor.
i had to do this to my truck over a year ago. it would move left and right with no issue. the up and down would either be excruciatingly slow, or wouldn't move at all. issue was resolved when i replaced the motor.