Robert,

The alarm horn is actually a seperate horn that differs from the car horn. You will notice it resting high on a bracket, dead centre near the firewall. To answer your question regarding the bulb, it doubles as lighting the rear ashtray and at the same time throwing some light on the inside of the armrest. It's been years since I replaced my bulb and the instructions should be in the owners manual. You probably pop the ashtray out (as you would if cleaning) to access the bulb...