The cover plate on the inside pries off with a screwdriver. There's a screw holding the electrical connector and three screws holding the mirror to the door. There might be a gasket or rubber strip so make sure that goes back properly.

If you have an oddball manual side mirror, there's a locking tab on the control knob. With the control knob off, pry off the trim plate and remove the three screws holding the mirror.

Sixto
91 300SE
87 300SDL
81 300SD