I had to replace the drivers window regulator in my '92 300e and at first it appeared that there was no way the assembly would come out through the opening in the door.

I figured out that after detaching all the mounting bolts and temporarily reconnecting the window switch, I could operate the regulator up or down (I don't remember which way) and change the shape so entire assembly (regulator and motor) fit through the opening.

Of course if the regulator motor is completely dead this won't work.