The alarm and the immobiliser on mine are separate things, I would have thought yours would be the same if it is after 1996 and not an import model. You can tell by the key.
Transponder keys.
The alarm is port or dealer fitted, I can tell you where the connections will be via pm. Not much point in removing it if it is working, as it would be so easy to bypass if it went wrong.
The immobiliser is a transponder chip in the key, and would be very difficult to defeat unless prepared, the ecu would stop the electronic injectors working. It should be very reliable, the weak point reliability wise is the key so be sure to have a spare with correct chip in.
I think you would struggle to stop anyone just coming along and winching it onto a recovery truck though.
Multiple barriers are the best way, if a car was to be stolen, the car would have to be broken into, and the alarm set off, then the thief would have to stop the siren, and the siren has an internal battery so would have to be broken apart to stop it, then the hazards would need to be stopped flashing, then the start inhibitor bypassed, then the steering lock broken or removed, then the immobiliser defeated. Add a couple of extra barriers such as a steering wheel lock or pedal lock and that would go a long way to put a thief off. The more obvious barriers the better. New cars don't have these mechanical barriers, that's why they seem to be easy targets at the moment.