Audio Systems: security reset, aftermarket stereo, air bags

Question
QUESTION: just got a 2004 impala, stereo is locked how can we reset?

ANSWER: there is no reset, and there is no code  
the radio don't belong to the vehicle it was replace and now you have to go to the dealer


---------- FOLLOW-UP ----------

QUESTION: will an aftermarket stereo work?

Answer
yes you can do that but you need a speacial harness, there is no other way to do the installation  
dont cut corners and try to use a cheap harness the vehicle will give you a lot of problems
with the cluster dash and air bags

http://www.oemautosound.com/c-135-gm-chime-retention.aspx