Classic impreza mirror glass and motor disassemble.
 

Right then, this is how I got the glass and gubbings out of my wing mirror.

Take the door card off.
unplug the electric window switch and mirror cable.
Take the triangular trim off that covers the rear of the mirror.
Undo the 3 phillips screws that hold the mirror to the door.

Now to get the glass out.
Don't try to pull the black plastic surround out with the glass, that doesn't work.
You need to warm the surround with a hairdryer in order to slip the mirror out of the holder.

My weapon of choice was the nicky clarke 2000W fuzz control. :D

Attachment 54774

When the black plastic surround is warmed up enough, slip a credit card into the edge and bend it under the glass.
Attachment 54775

Work it around and slip the glass out
Attachment 54776

This reveals the black plastic bit the glass sits in with 4 screws. Thats why you can't pull it out!!
Attachment 54777

undo the 4 screws in the middle.
Attachment 54778

and take it off
Attachment 54779

Next take the wires out of the plug. Write down where they go!!
A small screw driver easily pushes them out. (remember to bend the tabs out a bit when you put it back together).
Attachment 54780

Take the 3 screws out that hold the mirror to the door mount.
Attachment 54781

And pull the wire through.

Next undo the 4 outer screws on the motor bit.
Attachment 54782

and wiggle it out
Attachment 54783


Putting it back together is simple. Just do it backwards!