It was covered a few years back on this site.
Just did mine last week, mine had wood screws not bolts.
The arm should come off by a bolt under a cover under the arm.
With the arm and mirror removed the shroud will come off exposing the screws.
I could not get mine apart.
Another member suggested drilling 4 holes in the cover to access the screw heads and cover the holes with plastic plugs.
Either replace the screws with bolts or just snug the screws up.
http://www.irv2.com/forums/f115/loos...lp-105622.html