Factory Alarm System Upgrades

I have a 2005, DeVille DTS that just suffered a break in. The thieves smashed the driver-side window and did all the work from there. The never opened the door, and the alarm never went off. I would like to add a proximity and/or glass breakage sensor to the factory alarm. I really don't want to go aftermarket on the alarm unless it is a direct plug-in like the radio interfaces. Does anyone know the pinout and location of the factory alarm module? I'm an electrician and could easily design a circuit to add additional modules.

Bobby