You'll need a mounting bracket and the connecting wire. Those are both available online at a discounted price. Unfortunately they didn't install wiring for a changer in the trunk on our cars by default, so that will have to be done by you or someone who can do that sort of job. Good luck, and let us know how it goes.
The Infiniti dealer near me said that the 6 CD changer was no longer for sale; I could only get the 10 CD changer which is almost $600! I said no thanks to that. InfinitiParts.Net has a 800 number you can call. They seemed to be fairly intelligent the one time I called, so you might try calling them and asking if it would work. The problem is that you might get some guy willing to say anything to make a buck. Tell him you already bought one or something like that. Just a suggestion.