I just did this repair without removing the window motor from the door.

One important note is the inner door panel isn't held by clips, there are 4 or 5 plastic legs that slide down into slots. If you try to use a pry-tool the legs will break off. Remove the tiny screw from the bottom-center of the inner door panel, and push the panel upwards, the legs will come out of the slots without breaking. Of course, first you remove the lock-knob, the plastic cup at the inner door handle, the main door handle, the chrome door latch trim, and the window switch.

Then I drilled a tiny pilot hole in the center of the old peened stud on the arm, 1/2 way deep into it. Then I drilled it out with a larger bit just enough to cut loose the peened shoulder. Carefully knock out the old stud.

I peened over the stud in the new plastic slider by supporting the back side of the small part with a socket for a 1/4" nut. The O/D of the socket exactly fit inside the plastic hole in the back of the plastic slider. Then I backed the socket by hand, with a 2 pound auto body dolly. The 2 pound mass of metal absorbed the inertia of the hits by the ball-peen hammer, so the arm doesn't get bent.

You don't need to hit the stud very hard with the ball-peen hammer, the metal is pretty soft. Remember to put the small spring washer back on the stud before peening over the stud; I forgot, its too late now.

I made an alignment mark on the part that stops the downward movement of the window arm, and removed that part from the arm. Then the window slides down a bit further than usual so the slider can be put into the end of the track. Then put the stopper back on the arm.

I used a few dabs of contact cement to re-afix the plastic vapor barrier, and the door panel went back on just fine.