04 sunfire install question

gents, putting a viper 791xv in a 2004 sunfire (no oem keyless, no power locks). i have two questions: 1) which wire is the tach wire. i have seen different wiring diagrams say its ppl/white, orange, or white at the ICM (at the icm(top of engine) a wire of each of these colors is present!). which wire is the correct one?where else can i tap it besides on top of the engine? 2)what does the term 'domelight supervision' mean? is this a trigger wire for the dome light, or is in the actual domelight circuit? it is (-) on the car. can i connect this straight from the 791s domelight (-200mA) output, or do i need to use a relay to drive this wire? thanks!

another question, could this (-) domelight output on the 791 be tagged onto the passenger door circuit (-) input, this way when unlock is pushed, the car 'thinks' a door is opened, and will turn on the dome light using the BCM normal routine?