I believe there are a couple of slots cut into the plastic cover behind the inside door handle. Pry out the plastic cover to reveal a screw holding the door handle frame to the door. Pull the door handle frame and window switch out to reveal a big screw holding the arm rest to the door. There are two other big screws that you'll see form the bottom of the arm rest. On a 126, there is a piece of trim along the trailing edge of the quarter window that also has to be removed. The screws are along the weatherstrip. When the door panel is free, lift it up the out, not straight out.

Sixto
91 300SE