dismantling the wing mirror is easy, all you need to do is take it off, take the glass off by gently levering under the edge with a blade and cutting the sticky pad out, or even simpler just use a screwdriver and get a new glass. then under that through the holes in the plastic there are 3 screws, remove these and gently pull the mechanism out of the broken shell, then refitting is just the reverse, the hardest part is removing the glass, it's held in place by a combination of clips on the back, and double sided tape, refitting is simple just carefully press it back into position ensuring that the clips click into place, the double sided tape is not really needed provided that all the clips are still there, if it already has a broken glass in place then you will probably end un breaking it, sorry but that's the way it goes.