My system does arm and disarm the factory alarm. I remember putting a couple relays (5-pin) spliced into the right side door wires that lock/unlock arm/disarm.

And that's about all I recall. I'll see if I can dig up the wiring diagram. Or take a look at the wiring when the rain stops.

__________________
Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K