Greetings,
I can't give you specific answers to your questions but I wish you luck with the install if you go forward. It won't be cheap. You should be able to buy the basic radio from an Infiniti dealer, maybe a Nissan dealer. The Infiniti I30/I35s and the Nissan Maxima share some parts. If I can find the link to an Internet Infiniti dealer I'll add it to this post.
Have you tried any of your local radio installers? They might be able to assist you with an install. In my area there are a couple of places that will work on your car, with your parts, and charge you their hourly rate.
Okay, I found the link. Try "www.nissaninfinitigmcparts.com" (Omit the quotes.) They claim to offer factory parts at wholesale prices.
Good luck. Post your results on the forum.
Regards,
Shortimer
