Rear window guy,
I just did this on an '87 SDL, same door in fact. I had to take the window regulator out, to get it in a spot to hammer the rivet back in place. The CD recommends taking the whole window out. I was able to loosen the track that holds the back of the window in place, move it a bit and get the window regulator out. I had to disconnect the wires to the motor at a junction box in the top middle of the door as well. It did come out and go in then. I was able to replace the little plastic part and get it all back in. Be sure to check the motion of the window in the track (not too tight, or too loose to get crooked). Still working ( said with fingers crossed).