Its actually very easy. First disconnect the power to the alarm and disconnect alarm module from harness and start removing (disconnenting) the alarm connections from the car wiring. If you are lucky and had it installed by a proffessional, there will be "Scotch-locks" on the factory wires and all you will really need to do is unplug the male spade connections out of them and leave the Scotch-locks in place. If they cut the factory wires then you will need butt-connectors to secure them back the way they were or you can solder and heat shrink the connections for a stronger/ better connection.
I have stripped dozens of alarms out of vehicles and about 50% of the time it was a hack job from a "so called proffessional shop" May be you will be lucky and not have to reconnect the factory wiring.