1987 Carrera anti-theft

Vehicle Information: Model: Carrera; Year: 1987; Body Type: Convertible; Engine (type, size, modifications): 3.2; Total Mileage: 91000;

Being a relatively new owner, and my first Porsche, I'm nervous about taking it on my first long distance overnight trip. Short of paying to have the electrics tested and a new switch installed (I did not get a key for the factory alarm, and don't know if it works), is there a quick way to disable the vehicle to prevent and/or discourage a thief from driving it out of the hotel parking garage? Perhaps a fuse, or removing the DME from under the seat? Your thoughts are appreciated.