If you take a peek under your car and see an aluminum housing about a foot long attached to the back end of your transmission, that will be your overdrive, if you have one. I believe they were optional on all but the 123GT models, and boy, are they ever nice! As for lights and switches, I have seen a ton of variations on how installers set this up, from what looks like a turn signal switch that controls the OD relay sticking out of the right side of the steering column to push-pull knobs on the dash, to subtle "OD" lights on the dash when engaged. The OD is a nice feature when working, and is about a $1000.00 upgrade in my area if you hire it all done for you. It is encouraging what you describe in your post, as far as the possibility of having an OD installed. As for the rest of the questions, I'll defer to the others, at least for now, until I go take a peek at my parts car. I've got to remove all this stuff anyway, it won't hurt me to know how it works. (!)