well air bag wires should be in a yellow wire loom, so stay away from those, lol
some trucks require both gray/yellow wires to be charged but you'll have to check, easiest way is to peel back a smal section on insulation and juice the wire and see if the heat comes on, if so just put your ACC2 or HEATER wire from your remote start to that one. If you need to charge both, you just need a simple relay. Most remote starts come with an activation wire which you'll put to pin 85 on the relay, then splice a small wire off the ACC2 or HEATER wire from the remote start and put it to pin 86 on the relay. The take a hat 12v lead and put it to pin 30 on the relay. Last pin 87 goes to the second heater wire and your all set. If the remote start doesn't have the activation wire just ground out pin 85.
AS for relays they are actually quite simple little things
pin 85 and 86 are the pins that activate the switch. just puting 12v to one and ground to the other turns the switch on. I personaly always use 85 as the negative and 86 for positive, just so if i have a prob i can trace it back without getting confused. so basically if you have 85 grounded perenitly, every time you add 12v+ to 86 the switch will turn on and vise versa.
Pins 30, 87 and 87A(one 5 pin relays only) consider 30 to be the middle pin in the swicth. 30 can either be connected to 87 or 87a. so when you activate the relay pin 30 and 87 have continuity. When you de activate the relay 30 and 87a have continuity. You will always use pin 30 for a constant 12v+ or ground depending what your doing. generally 87a is used for things like starter kills for alrams and such, pretty much you'll mostly use 87.
as far as the neg lock, you may be right i did mine about 3 year ago so i can't remember, just make sure you use one of those test lights with the LED they are way better. and also make sure that when you test the wire you get the pulse from the appropraite dirrection, like lets say you ground the end of the light and probe a wire and hit lock, it lights, cool, but makes sure with the same wire probed, if you take the light off of the ground and hookit to 12v+ and hit unlock it don't light, cause if it does you may have reversed polarity locks and those suck. that's why the LED test light is the best, cause it lights green for NEG and red for POS, a little easier to use, less confusion.
hope that all helps, let me know how it goes or if you get stuck, i'll see if i can help you out as best i can.