I've yet to touch an OnStar equipped GM yet (I'm not getting involved with those).
But on the newer GM's (IIRC, 2002 and up), they need a different wiring harness for the radio then the standard Metra 80-1858 wiring harness. They use the GMRC-01- without which, you will lose your door chime and domelight when a door is open. Also on the stock radio's there is no accessory wire- to install an aftermarket radio properly, without using the GMRC-01, you'd have to drop the steering wheel panels and tap into the ignition harness for a turn on wire.
Your truck might not need all of this however, since it's an 00.
you need a metra **-1858 harness... a dash kit which is a metra 99-3002... and metra 40gm10... or the equivalent... also... is it a bose system? if not... drop the glovebox and look behind it to the right... is there a metal box with a harness or 2 plugged into the side? if so then you have a factory amp... i usually bypass those but you MIGHT be able to use the remote turn on wire in the harness and play it through that amp... but i wouldn't...