Adding DIC / Audio Controls post purchase

I would like to add DIC/Audio functionality to an LS 2003 burb which did not have driver convience package installed.

the 3rd page of the following link has some good info on what's needed for DIC, but nobody has attempted the audio from what i understand. Anybody here done it / know how?

http://www.gm-trucks.com/forums/index.php?showtopic=17291&hl=steering+wheel+controls

thx in advance
-brad