You can connect it via a 3.5mm "aux" lead. If you buy the CD-changer to aux lead adaptor to plug into the back of the headunit. No idea how much these are, PM a guy on here called Matt (username MT_Audio) This lead is only compatible with the tuner/update list stereo (can't rememer which one!)
In short, get a non-chavy non-ripspeed decent brand Headunit and it looks ok. I had a 2009 era Sony that fitted in really nicely with it's orange/red buttons (they did look quite bland back then, which was a positive) Modern Alpine units look alright too if you get the red/orange backlit ones.
EDIT: Or you can get a "Renault Tunepoint." Think these are about £50, they sit in your glove box and allow you to connect USB/aux/iPod USB cable. Again these plug into the 6-cd-changer part so you need a tuner/update list stereo (again, can't remember which is which)