Hi there, I too need info on the alarm wiring of a 1992 300E

To your point of not much info on the CD, I learned something today too, for alarm system info:

load disk #2
go to Chasis and Body
go to Electrical Systems
go to 82 body
go to 0980 Function information
or
go to 0983 alarm system testing

The testing procedure is a must for troubleshooting faults or problems.

Unfortunately I have not yet found the alarm system wiring diagram. If you happen to find it please let me know.

Hope this helps,
Acky