Putting my process here since it was a little more difficult than expected for what I thought would be a very simple job and there weren't really any sources available online to reference and confirm what I was doing. (I have an 1991 240 Sedan)

This is the process I used to replace the interior door lock release lever (interior door handle) casing. My driver side casing was shattered when I got the car and the passenger side was cracking so I needed to replace them--90s plastic doesn't age well. I purchased an aftermarket replacement from SwedishCarParts, they have both driver side and passenger side available; Voluparts also has OE ones available (as does VolvoPartsWebStore) but I guess Volvo only stocks black ones nowadays.

Here is the process:

1. Use a plastic pry bar (or screwdriver) to remove the casing frame
2. Remove the door card and moisture barrier(lots of guides on this forum for that)
3. Remove the casing
   • If it's damaged it'll probably shatter enough to get it out, otherwise it's a clip-in
   • The front portion is a long tab that slides in a hole in the door and the rear portion is a clip that you must bend inward to install or remove.
4. Remove the lock release lever ****
   • I you don't care about damaging it, use brute force
   • Mine was very stuck and I didn't want to damage it with pliers so I sprayed silicone lube up inside, then wrapped it in a wet washcloth that was microwaved for 2 minutes and it was able to come off very easily by hand
5. Slide the replacement casing over the metal tab that the **** came off of
   • There's a slot in the bottom of the casing where that metal lever slides in
   • Driver and passenger side casings are not interchangeable, the slot on the casing has a circular pin at one end, that pin should be oriented towards the front of the car
6. Before fully installing the casing, reinstall the metal lever's plastic ****
7. Install casing and reinstall all removed door components--Done!