If it was the remote it wouldnt unlock the doors..so we can cross that out (Unless you have a button the remote that unlocks and another that dis-arms then it might be the remote)..what i would do is talk to the people that installed it ask where they put it (if they remember) most places would be right under the steeringwheel,unlock it and pull the fuse out and you SHOULD be able to drive it..im not sure of the specs on your alarm (IE wont crank if the alarm is engaged) and see if they can put in another brain to see if that fixes it
There's a start