There is a triangular plastic piece of trim on the inside of the door. This has to be prised off (carefully as it is easily broken). You now have access to 3 no.screws which attach the mirror to the door. You need either a big Phillips screwdriver or else a 10 mm socket and socket wrench to remove these. Easy enough to do. If the mirror is heated, there will be cables to be disconnected also.
If it's just the glass that is broken, you can take that out without taking the whole mirror off. There are plastic clips on the back of the glass which hold it onto the swivel - again this can be prised off carefully and the new glass pressed back into place.
JD, January 2008
