Hi bunter,
Few points about the car and some solutions. Auto will keep on going as long as it's serviced regularly. They're a strong box and will hold up. As for the door ajar light, check the Centeral Timer Unit. (as labeled) It is under your dash...just above the fuse box. It may have a loose connection. It should just snap into place. Maybe it's come loose?
In terms of smartlock etc, the aussie cougar's come standard with alarm. You need to 'double' lock using the remote to activate it. I'm not sure if this can be done with the key in the lock (anyone confirm this?)
Performance exhaust will free up a few bit of horsies. Professorsabre should be able to confirm this as his beast is an auto too
(btw Ang, i was in Adelaide last week! Didn't have ur number so i couldn't catch up!)
Cheers
George