Brain dump time.
There seem to be 2 DCM types, and 2 doors (i.e 4 types) and some old versions.
The basic version supports basic non folding mirrors - but I cant remember whether the basic versions support dimming
The other version supports folding, memory etc etc. IE if you have folding or memory, the DCM supports dimmimg and dippoing (again, from memory. probably right)
The DCMs connect to the canbus, and can be coded to think they need to do dimming, dipping (dropping) or folding dependant on the mirror connected.
The mirrors that support dimming mirrors have a different conenctor for the mirror glass to the non dimming one (more connections unsurprisingly)
So, you need a mirror frame/mech that supports dimmimg (to get the extra wires) and the dimming glass
Car may then need coding as-well - depending on what is programmed in the DCM
Door panel. Remove screw and round plastic bit around door lock
Remove mirror quarter panel (unclips from window edge)
Remove covering on the handle you pull when inside car, to reveal screws
Pull off door panel round edges- may be worth buying some extra door panel clips incase some break or look worn - always worth replacing them if they break, or door panel may creak
Pull upward, whilsty holding the rubber groove at the window edge in place so it doesnt come off.
R