Well, I partly anwered my own question. Found this on crutchfield.com:
Just install USA SPEC's iPod interface — it not only allows you to listen to all your favorite tunes through your car's speakers, it even lets you control song and playlist selections right from your radio.
Just mount the compact interface box in a hidden location in your vehicle, and connect the adapter cable to the CD changer input on your compatible 2001-up Volvo factory radio. Plug your iPod into the interface — you can control volume, source, song selection, and up to five different play lists right from the radio. And the interface charges your iPod while it's connected! (Note: the adapter is compatible with all iPod and iPod mini models equipped with a dock connector and iPod software update 2004-04-28, or higher.)