Just repaired both of my mirrors (1999 e430), I suspect they were damaged by children grabbing onto them when learning to skateboard. FYI I did not need to remove the mirror glasses, with the mirror folded back I could reach inside and unclip the vertical spring bar that retains the cover. Then with the side of the mirror close to the car pushed in the cover will slide off, it jams at around half way off but if you move the mirror to the other extreme then it will come off. The hardest part was reattaching the springs.

Great suggestion, thanks,

Peter