I swapped side view mirrors
once - and this was a non-power mirror. Keep in mind the following is all from (less than perfect) memory

:
Remove the door's inside trim panel -leave door open so that you can get to both sides. Think I rolled window all the way up. The mirror is held to the door's outside skin by two (10mm wrench?)nuts. I used a 10mm(?) box end wrench and loosened the nuts until they were almost ready to fall off the studs.
Next, hold the mirror with one hand, and squeeze your other hand into the door so that you can remove the nut - not dropping the nut inside the door is the tricky part. Ditto for the other nut, after you take a deep breath and are ready to go at it again.
Installing the mirror is similar - hold mirror with one hand and carefully start one of the nuts with the other hand. Once it's on, take a deep breath, and put the other nut on. After that, you can kind of relax - the hard part's over with. Tighten both nuts, first by hand and then by wrench. Reinstall door inside panel.
That's what I remember doing. Hope this helps
!