Just replaced the non-powered wing mirror on my 1999 focus using the above answer, which covers just about everything.
My only added points are:
Removing the mirror control was a bit of a hassle - I levered the soft "Joy stick cover" off with a flat screwdriver and broke one of the lugs on the actual joy stick in the process - didn't matter as the new mirror came with a new joy stick. The joy stick then slips out from behind the housing.
You still need to take the door card out to get at the 10mm bolt which holds the wing mirror in place.
When removing the door opener insert, you don't need to disconnect the powered window control - I couldn't work out how to do this - turns out it doesn't matter, if you "pop" the control forwards it will hang loose across the opener insert and you can manoeuvre the opener insert over the opener whilst holding the opener in the "open door" position.
The opener insert plus the door card can then be left to hang whilst you get at the mirror bolt.
To replace the mirror joy stick and joy stick cover, fit the joy stick into the housing first (make sure the control is the right way round! i.e. joystick up = mirror angle up etc.) and then slide the joy stick cover on from the other side of the housing aligning the cut outs with the lugs on the joy stick - twist the joy stick cover 45 degrees (i forget whether Left of Right) and it will lock into place. You can then remount the housing into the door.
Dan Cook, December 2007