YEAH!!! I did it -- the radio is now unlocked and working fine.
Here is the secret to share with other people -- For GM cars, get the six digit number from your radio system. Then call the 1-800-5375140. Chose the number matching your car (1 for Chevy). Enter the car number + 06010 + *. This automated telephone will tell you the code nuber (4 digits for my car). Enter that 3 or 4 digit code into your radio system. Now you are ready to rock......