if you have little or no experience with alarm systems, do not attempt to mess around with your vehicles wiring! the consequences could be as little as a popped fuse, or worse, damaging your vehicle's ECU or possibly a fire!
my suggestion is to take it to a mom/pop shop, or even better Best Buy or Circuit city as they warranty all their installs lifetime! and you dont have to worry that either company will go out of business down the road.
instead of paying them to remove the alarm, pay them to install a new one!