I recently had to replace my cracked mirror, housing bezel, and turn signal lamp as well. Part numbers listed are for passenger side 2023 Bolt EUV Premier (with camera). Here's a write up on the steps used:
Step 1. Remove the side mirror glass & backing plate (part number 42779382).
The mirror glass (with backing plate) is attached to the side mirror motor by 9 plastic tabs (motor attachment points shown with arrows in the picture below Step 4). Adjust the mirror tilt all the way down to expose more of the mirror & backing plate edge. Firmly grab the mirror and pull it away from the motor housing to release the plastic tabs (you may want to tape the front of the mirror to avoid being cut by any loose glass shards).
Step 2. Disconnect mirror wires. After the mirror plate is removed, disconnect the 2 heating element wires and the side camera cable (if equipped). I used a small flat head screwdriver to gently pry & release the camera cable connector (you don't want to damage that).
Step 3. Transfer the 2 metal stay position pins from the old mirror to your replacement part.
Step 4. Remove the housing bezel (part number 42779359). There are 4 T10 screws (circled in the picture below) holding the bezel & other plastic mirror caps parts in place.
Step 5. Remove the mirror caps. This is just held on with plastic tabs. There are two upper mirror cap pieces - one is painted & the other is unpainted (pointed to with arrows in the picture below). The two can come off together.
Step 6. Remove the side turn signal lamp (part number 42744827). Unscrew the 2 T10 screws and disconnect the turn signal connector (circled in picture below).
Reverse the steps above to reassemble.
