[Silentalero]

you don't need to drill into your interior... run the wire through the engine bay, and look for a small spot in the firewall where all the other wires go through. Cut off the switch, and slide the wires through there. Then just reconnect the switch and you're ready to go. I wouldn't tap into the other headlights, I would wire it to a fuse, or if it has a fuse inline already, you can wire it to the battery.