Thanks to 004Gunner for his writeup, as I followed it nearly exactly except for a few minor changes.
Installed Rear Lights

The fog lights I recently installed also came with a set of simple 2"x5" 55w halogen driving lights. I've long wanted a pair of rear-facing lights to augment the stock reverse bulbs, light up the area when in the sticks, and, when necessary, ward off tailgaters and drivers who don't understand their high beam/low beam switch (although this last part is technically illegal...). I attached them to the rear bumper, using two holes already present and drilling two more.

Like 004Gunner, I purchased this 3-position (on/off/on) switch for the dash:
Scion OEM Style Rocker Switch
And I did my wiring following his diagram, mounting a relay behind the driver's kick panel and running the wires under/behind the driver's side paneling all the way to the back and to the outside, just using zip ties to keep it neat. This involved tapping the cigarette lighter power wire (gray wire) so I can trigger the lights manually when the key is in using accessory power, and tapping the reverse light wire (red wire w/ yellow stripe in 2000) behind the kick panel so the lights would come on when in reverse.

The only real difference that I could see is that instead of going through a grommet in the back to get the wires out of the cargo area and to the lights, I simply ran them out the vent behind the driver's cargo-area panel, which comes out right behind the mud flap. Also, for the wire from the battery to the relay, I already had a tiny hole in the firewall where the power wire for my alarm comes in, so I used that as my entry point.

Here are pics:

Before


After


Manually turned on


Shifted in reverse


As for the other part of this thread's subject, I managed to short out power to the whole truck because of how I connected to the battery. I installed the lights on Sunday, and on Monday I was playing with them by flipping them on and off without the truck running. On one of my flips, I heard a loud click and everything went dead, as in the entire truck - no lights, no door ding, no accessory power, nothing. Turning the key to start the truck resulted in nothing, not even a starter click. After a few minutes some power came back, but it immediately died again when I tried to engage anything electrical. Stumped, I jumped the battery and drove around for a few minutes, but there was clearly something wrong because everything electical seemed to be struggling. My dash lighting even flickered in sync with my blinker when signaling a turn and there was a weird whine from the engine. I got back home, and when I turned the key off, all power was lost again.

After retracing all of my wiring steps and feeling confident I had everything right, I disconnected the negative battery cable and then the lights' power wire from the positive terminal. When I reconnected the negative terminal, I immediately had full power again. So it was clear the problem was in the connection to the battery. After staring at it for a few minutes, I realized I had connected the power wire to the bolt on the positive cable marked in red in the pic below, when I should have connected to the bolt actually on the main positive cable. I'm not an electrical expert but, but I assume that the way I had it was creating a short, or an arc from the main cable over to my connection point, so that whenever I drew too much juice it would short out. I moved the lights' power wire over to the main screw, and so far have had no further problems.

Battery (I know it looks nasty, cleaning it is on my to-do list very soon)


I'm very happy with the lights. They really help me see better when backing up at night, and I like having the ability to trigger them manually whenever I want.