Need instructions for RDS radio

I have a 2006 chevolet pickup. I'm installing a radio in it. It is a RDS radio and I need to know how to get the six digit code from it. Can you help?

Go to the dealer,has to be programed with the Tech 2 and GM started doing this in 2001.

Thank you. I have a appointment on thursday. They told me it would cost $30.00