2003 HD Radio Information

Hello,

I have a 2003 1500HD Silverado. I have the radio with the AM/FM/XM 6 CD changer. I notice that the button to change to CD says CD/AUX. I am assuming that this would allow for a seperate input such as DVD or MP3. I would love to use my MP3 player in the truck. I don't see any input jack location, so I am assuming that there is not one built in.

I have seen an item online (offered by GM) that plugs into the back of the radio to allow another input through the CD/AUX button.

How do I remove the radio to get to the back of it? And does anyone know if these components that plug into the radio work well?

Thanks!