i done it the other day and found the easiest way for me to do it was:
fold the mirror in
look for a slight gap between the cover and the textured plastic bit(any gap will do) wedge a screwdriver in and pop it out a bit
pop something in as you go along to stop it popping back in
then move around and pop the cover off bit by bit until you can get a grip of it and pull it off, or you will hear the clips popping off then it will come off itself.
oh and when putting then back on watch for the clip closest to the car, i found it to not line up properly and needed to push down on the top to get it lined up.