Eric:
My 05 16' came with a Sony radio. There are several ways to connect an iPod to it, like an FM adapter or a cassette adapter. You can also add another box that Sony designed to allow other devices to play through the radio, called an XA 300. The link below shows this item. I added it, and it can play not only the iPod, but also a USB so I can play my computer (like watching a DVD movie) through the trailer speakers. It is pretty easy to access the radio, and I mounted the XA 300 on top of the enclosure using velcro. You can also splice into the 12 VDC wiring and put in a socket so you can keep the iPod charged while keeping everything contained in the overhead locker, or you can just plug it in to the cigar lighter under the dinette table.
http://www.crutchfield.com/S-Pu4WVIE...300&i=158XA300
Please let me know if you have any questions.
Bob