I also have to replace this cover. I have not done it yet, part is on order. I asked a friend who is a mbz Tech. in our case the screw is exposed, well at least on my 92 500 it is. should be on yours also. anyway i asked the same question about replaceing this visor cover. here was his response. Hope this help. Also Please get back to me and tell me what you did and how things came out.

"There may be a snap on cover at the pivot point of the visor.
If it is there, you can remove the cover with a small pick or sharp object.
This will expose the screws.
Once removed, you will have to pull the visor gently out to expose and disconncet the electrical connector.
Some have the connector, some dont because they make contact with a metal tab kinda like a AA battery would"