I think they're the same mirrors as on the 159, if so, pull the glass out, if you can get a suction cup, this is ideal to remove them without breaking the glass.
To echo armoor above, the mirror caps are held with 4 tangs which protrude through the back of the mirror, all visible and within reach.
Once you've disengaged them, with a screwdriver or similar, you need to pull the cover backwards, and rotate it slightly downwards so it clears the mirror pivot point and remove.
The plastic has a bit of give in it, so it will flex - the trickiest part is getting them back on.
Posting from my phone - excuse spelling mistakes