Bumping this old thread to thank smartinec for his details.
I am having the exact same problem with the door. Like him I was finding it impossible to remove the set screws - now I know why, I need 7/32.
And I also know I need to replace the motors.
The one question I have: when you replaced the motors did you transfer the capacitors over? Can you do without them, or do the replacements come with them fitted already?