can I fix my radio/cd unit in my truck?

I have a 2002 GMC Sierra SLE truck.It has a factory radio/cd unit in it now.It continues to come up with Err on the main screen. Can hear little motor running inside the unit but when putting in a cd. It kicks it out. Radio works but still says Err on screen. Can I fix this or what do you think may be wrong. Was working perfectly until I was driving home and it stopped working.

Lynda
January 2009