2004 Sierra Keyless entry ?

I an tying to install a keyless enrty in my 04 sierra I searched and read some posts but didn't see specifics for my year.  I am assuming from reading that the wires I need are behind the drivers kick panel.  There are two wire harnesses back there and I am trying to figure out which wires I need to cut to install the keyless entry.  I used a voltmeter and checked but didn't see 12v on any of these while pressing the unlock/lock switch.  Some had constant 6-7v on them.  I guess the days of 12v are over.  Are these a low voltage drive or switch to common?  I have a 2 door (I think this matters) and the truck does not have keyless entry from the factory just power locks.  If they are switch to common, can I just short them to ground to test them?  I already broke one of the door panel tabs trying to get it off (I still haven't something in the lock area is holding it on yet) and would prefer not to blow up my computer to install a remote entry box.  Thanks for any help.

An Update from this morning, the wire harnesses behind the driver kick panel are not connected to the power locks.  I disconnected all 3 of them and the locks still worked.  I found one wire coming from the door harness that appears to  change states when the button is pressed.  This  wire is a brown wire and it appears to be the only data wire.  There is a 12v continuous (orange) wire that when disconnected stops the locks from working and of course a black ground wire that prevents them from working.  But the brown is the only wire that does anything when the button is pressed and that appears to be a short pulse.  Shorting this brown wire to 12v or Grnd does not trigger the locks.  From the circiut boards in the control module I am guessing the locks are controlled by a pulse from the computer and the solenoids are behind the door panels which I can't get off.  Any thoughts or does anyone know where I can buy the factory service amnual for this?  Thanks

use a DEI 456G  or u can do it the hard way..which i dont recommend cause it takes forever...but the lock and unlock are grey and tan and they are reverse polarity.  you have to find the wires in all 4 doors and in the rear hatch.  so ur looking at using 10 relays and alot of complicated wiring.  ive done this before and it sucks...just use a DEI 456G