I've got a diagram, but the file is too large, so give me your email and I'll send it. I got it off of Mitchell On-Demand, which I haven't had to use often yet, so I'm not sure just how accurate it is. But everything looks sound.
I also looked at the electrical component locations, but regarding the back-up light switch, it was quite vague. It only said that the switch is on the right side of the transmission, regardless if it's A/T or M/T. It should look kinda like an O2 sensor, basically a little plug with wires coming off it. I had the same problem on my 5-speed Sonoma and this was the fix. It was real easy to change out, and the part was only like $10. You basically needed a socket and wrench to remove it. I'm not sure on Toyotas though. Sometimes (at least on GMs) these switches fill up with oil, and will not turn on the rear lights when shifting to reverse.
