First off, thanks to Timgco for sending me the black mirror caps, spare DS mirror and the lights.
This has been covered before, but I'd thought I'd share my experience replacing the caps.
As Paragon advised, use remote and turn both mirrors inward. Then firmly grasp the outside of the mirror and pull off. (The DS popped right off with little effort) Being careful to work around mirror if it does not pop right off.
Use a small screw driver or finger to gently push the tabs on the old mirror cap away from center while using your other hand to pull the cap off. You may have to work around the cap, one tab at a time.
After struggling with this and the cap still not coming off, just pull like hell and it'll come off. It turns out GM sticks some nasty two sided tape on the inside to help hold the damn thing on.
Don't worry about the tabs. If you did as I instructed above, most will not break. I didn't break any.
Use more two sided tape on the new cap, I used velcro, so it'll be a pain in the ass next time, too.
Slide cap on and it pops into place. Press firmly on the area covering the tape or velcro to make sure it'll stick... real nice, like.
Pop mirror back on gently working around it so as not to break it, either.