I added the red switch to shut off the interior lights and running board lights. It is a simple SPST switch from Radio Shack.

Another shot of the switch with the access panel removed.

This is the Central Junction Box. It is behind the panel near your left knee. The wires I cut come out of the top rear of this fuse block.

In order to get to these wires, you need to cram your head down by the brake pedal and look up towards the fuse block. I believe I had to remove some of the tape around the wire harness to access the wires. You are looking for 2 black w/light blue stripe wires. One goes to the running board lights, the other to the interior lights. These wires originate from the same place, so they can be hooked to the same switch without problems. I cut and joined the pair, ran a lead to the switch, then back to the black w/light blue stripe wires that run into the vehicle. You need to run 2 switches if you would like to control the running board lights and interior lights seperately.

I hope this is clear enough to be useful. You can see where the black w/light blue stripe wires originate in the Central Junction Box. Click on the picture to see the high resolution version.