I disconnected my negative lead yesterday, and everything reset per the book on my 2003 SLK230 but the radio. I thought I had the correct code, and I was given the same code by the dealer when I called service. I did buy the car used. And by the paperwork I have, the CD changer was replaced in 2007. Would there have been a face plate or some other part changed that might of effected the original radio code? I have put the code in, hit OK and on the 3rd try it puts me in wait mode. Now the OK button is the button directly under the OK on the LED, right? One other sympton and I don't know if it is a problem. When I turn the car off, with the radio on, it continued to play, even when the key was removed and the door opend and closed. Itdid shut off after an hour if allowed to continue to play. I don't know if this is related to the security code not taking?

I hate the thought of having to take this to a dealer now.
Any thoughts on what I should do?
Gapblais