First off, I'm a complete novice when it comes to car audio and it's
terminology but here goes - be gentle )

I've got a Pioneer KEH-P6900R (that's what it says on the removable head
unit anyway - I've got no idea what's behind the dashboard that this head
unit plugs into) and I've also got a Pioneer CDX-P25 6-CD changer unit in
the boot that's controlled by this head unit.

I want to go DAB so that I can listen to stations like Planet Rock etc., on
the move. Is it just a question of changing head units and still being able
to keep the CD player and existing wiring, or, as I suspect, will I have to
change everything?

Cheers,

John.