I just did this on my x7.
something that made life easy: simply taking pictures of the pieces as I went with my phone, before pulling wires and after.
- aim the mirrors fully upward
- start from the outside lower corner
- use a wider trim tool (shoot for around 2" wide, over under isn't a big deal)
- press against the mirror over where your trim tool is pressing upward
- breathe, don't rip it off
You're going to pop it off from the corner and work your way inward along the bottom. Once the bottom's free, feed your hand in behind the mirror and see if you can pop it off--there's a real good chance you can.
passenger side mirror:
driver's side mirror:
keep an eye on what cables go where. for the outside light element's wire harness, you press down on the obvious tab on the harness, but then press the dark black plastic retaining tab down and it'll slide free easily. You can see the retaining tab in the passenger mirror picture pretty clearly (below the triangular element that is your blind spot warning light)
here's what we call a pro gamer move: have an assistant catch the caps as you pop them off and they suddenly take flight. No assistant? put down towels because they'll go flying.
yours are very likely like mine since all three odd-number models can rock the same mirror kits. You want to feed a screwdriver/prodding pokey thing of your choice in and press the mirror cap retainers -outboard- to release them. it might help to have a smaller trim tool wedged in around the outside of the cap. The holes you're poking into are at the top left (inboard and up) and immediately right (just outboard) of the circular motor in the picture above.
popping the glass back on is fairly easy. just remember you have it at an angle, not perfectly vertical.
if anyone's swapping for M mirrors, the 5 little torx screws (iirc, they're a size 9) are visible here and the surrounding ring pulls off easily, remembering there's a little catch on the inboard side right over the pivot, so bend the mirror back before pulling the surround off to replace it.