Push the mirror rearward
Look in the gap, there is a wire bail retained on a tab
Stick a screwdriver in and pop the bail off the tab
Pull off the shell

If you want to remove the entire mechanism, it comes off from the outside, remove the screws holding the mirror frame to the door, and unplug the connector, once you have the shell off.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech