OK.. the only difference would be the XM if you have it. 04's are single cable and 03's are dual.
The OnStar antenna wiring feeds down through the right A-Pillar and over to the module. there should be a cable each.. one for the phone and one for the GPS.
The RSE diagram in the link I posted should show the wire colors for your connections.
Since your adding this, you may need to order some terminals (#12089649 ($8.80 /10 Bag)), unless the wires have the connectors on them. If so, the RSE audio wiring connects to
SP250, which is a
shorting connector between the left of the airbag/glovebox and the right of the radio/hvac frame.
The DATA connection goes to
SP207 (2 consecutive posts), which is way over to the area of the parking brake pedal assembly; a flat-black connector.
Audio (3), DATA (1) and power (1). Then a ground besides the one with the audio. Remember, the diagrams will expand so you can view them better. How, depends on your browser's image viewer access.