I'd say the alarm has a fuel pump shutoff, and that has been improperly wired into the parking lights that the alarm flashes.
I'd also say, don't rip the cluster out until you've changed the dimmer switch/knob on the dash right under the cluster. I'm guessing that's why your interior lights shut off.
Those are minor problems if the rest of the car is in good shape.
I would also request a wiring instruction sheet from the alarm manufacturer to see if you can fix what the airhead installer did.
Remember, he got this car for "dirt cheap" which means he'll definately get his money out of it!
