I'm in the same boat, just bought a vito and no alarm.
I've read biguns post on how he installed a merc alarm.
can i just ask, how many components are required?
I have a 2012 facelift 113. so i think the latest looms will do, I've not contacted merc yet so have no wiring diagrams etc.
also whats the rough price of everything needed, i know the alarm was £290 fitted when new, but is is mega bucks for the individual components? Just I've spent most of my stash buying the bugger.
Not worried about part no's, just looking stupid if merc quote more than i can aford
cheers
paul