I have made this repair several times over the years on my 81 300SD. I always drilled out the old rivet, used a nut-socket-ball peen hammer-cold chisel, and flattened out the head of the new rivet. Then I took the arm to the door and slid the plastic slider in the metal guide. Worked fine.

I also had a 75 (I think) 450SEL and MB actually made the plastic slider so that it could be easily replaced. Not sure why they changed it later.