Your local Car stereo or car electrician is the best source of advice here. The choice is endless.
You could fit an aux input (ideally with a power connector) , in many forms, or you could fit a bluetooth connection straight into your DVD unit.
You need to be mindful that 13 years on, the original options were a little...."of their own time." And, likewise, anything you fit ought to be suitable for what the next five years throws at us.
It all comes down to what you want to do, apart from playing music, and how much you're prepared to pay.
To some obvious questions: are you happy with your car's existing Navigation system, which isn't voice activated, a real time system, nor up to date in terms of roads and addresses, are you happy with telephone operation (if you have it), and how do you really want to control any music: by voice, or by steering wheel buttons?
Myself, I'm a cheapskate, and I use a £30 bluetooth adaptor connected to an aux in to do satnav, music, streaming - all voice activated. But others spend up to a grand putting in other interfaces or replacement Comand modules
