The covers are removable and all that is needed is a flat screwdriver.
Here are some pics using an extra mirror I have:
Begin by inserting a flat screwdriver on the top or bottom of the frame that is next to the cover. I prefer the bottom edge since it is not as visible as the top edge should you mark/scratch it -
Gently pry the frame up around all three sides of the mirror housing until you completely remove it -
With the frame removed you will see the tabs that hold the mirror cover in place -
Using the screwdriver pry the tabs up and pull the cover out slowly -
Here is a pic with the cover and frame removed -
To reinstall you first install the frame and line it up with the notches on the housing -
Lastly, take the cover and slowly insert it back onto the housing. You will hear it click several times as the tabs latch onto the mirror housing -
Thats all there is to it.