Welcome new potential Fit owner
I bought the Navi because of the extras that came with it (VSA, audio on steering) and the fact that I've never had navigation and have always wanted it. I like that it is built in. Yes there is an auxillery port below the dash. Personally, I am getting the "clear bra" paint protection. It is kind of expensive but my old fit had a lot of chips on the front. So far, my milage gauge is showing 40.8 and I am almost through 1 tank of gas. Hope that answers some of your questions. There's lots of help here. So ask all you want.
