Do you have any idea how you would fit a tuner (if we were to get one) behind the head unit?

The tuner is a completely separate module, not too large (maybe 5" in it's largest dimension) and it can be located a foot or more away from the plyer. If you can find any sort of "hole" inside your dash, you can stash the tuner there and just run wires to the antenna connection and to the back of the player.

tanstaafl.