There was one when I did it! That's the thread I can't find. I did however save a screenshot of the diagram. Credit to whoever worked it out, IIRC a few of the Infamous guys contributed to that thread (looks like Kurruppt posted this picture). If anyone with better google-fu than me finds the actual thread, let me know! I couldn't find crap.
I remember I put mine together and found that both LEDs were backwards, but I don't remember if that was my mistake or if the diagram had them backwards. Something to check with it hay-wired before it's all soldered up. And obviously be careful poking around in connectors that go straight to the computer--I don't know what would pop if something shorted at the check connector, but I doubt it would be easy to replace.
I didn't have a plug end for the check connector, so I got some small-ish male spade connectors, trimmed them down slightly to fit, and put a dab of hot glue on each to hold them in place. There is almost certainly a more elegant solution, but this has held up, it's reversible, and it did not require hacking the harness. If I did it again, I might consider gutting one of those Snap-On adapters, or just buying a connector and pins (if not the whole assembly) from KivPanther.
I mounted mine through the blanking plate for the hardbody under-dash e-brake. It's out of the way, it's removable, and I can see it from the driver's seat.