My Cherokee had a car alarm installed by the PO, and I had to remove it. Without knowing the alarm and how it was installed, here is how I would go about removing it:
Find the alarm control box (look under the dash on both driver and passenger side).
Once the alarm control box is located, trace all the wires from the box and disconnect them. There may be a couples of wires that are spliced into the factory harness (spliced into the ignition wire), reconnect those wires.
That should do it.
MichiganTech Mechanical Engineer Alumni
1994 Wrangler Sahara - Jeep Project
2003 Dodge Ram 1500 (new truck)
2007 Mazda CX-7 (the new commuter car)
2005 Mitsubishi Lancer (Rear Ended - TOTALED)
1998 VW Beetle (SOLD)
1988 Jeep Cherokee Limited - (SOLD)