I am looking to get an '03 G35 sedan (automatic), what should I know about when I'm looking at different options?

I am coming out of a '98 A4 2.8 Quattro, I know all of it's dirty little secrets, I'd like to know about the Infiniti's now.

My main questions are:

• How is the navigation system?
• What is included in the sport package?
• Are there known gremlins or TSBs to inquire about?

Thanks for any help.