Brad,
This happened:
http://www.toyota-4runner.org/4th-gen-t4rs/99667-fried-ecu-wire-harness-2-months-later.html
What's very funny is that I'll be installing the very projectors that fried that fateful day sometime soon (this or next week). I had those retros redone recently.
After that sickening ordeal, when I approach a "mod project", I study it. Intensively. Before interior panels come out, I have everything drawn up (literally) so I don't screw up. If a project is too "electronic intensive", I walk away. Also, I've learned how to use a multimeter. I've learned to respect the electrical system and not "do things half a$$ed" (bad wiring/bad craftsmanship/etc). When I come at a difficult part of a project, I don't soldier on, I stop to asses what's happening and where I (if) went wrong. Works. I can't tell ya how many times this saved my butt.
So yeah, I feel for the OP. Tough lesson learned.