Audio Systems: dodge infinity sound question, dodge ram 3500, auxiliary input adapter

Question
I have an 07 Dodge Ram 3500.  It comes with the Infinity sound system.  It does NOT have any type of Mp3 connection.  This was apparently the year they were making the switch, as the 08 model does.
Is the ANY way to connect an Mp3 player (standard 1/8 inch RCA phone jack, I assume) to this system?  Maybe a port in the back that I don't know of.  I wanted to ask before I started taking it out of my dashboard.  
Thanks very much for any and all tips,

Anthony

Answer
You need the auxiliary audio interface for dodge chrysler radios,
your factory radio needs to have a mode button for this device
dodge auxiliary audio input
http://www.oemautosound.com/pc-298-149-pie-chry04-auxs-dodge-2004-2008-auxiliary...

and this is the cable jack
http://www.oemautosound.com/pc-663-149-dashmount-35-aux-input-is335-pac.aspx