My FM Transmitter " solution " is a basic option (admittedly), plus not elaborate, such as the suggestions provided above by other members.
Especially if you do travel extended distances, plus as you say, are most likely to pickup interference on the FM channels. I know it's an "old skool" solution too, but worked for me.

To be honest if you are considering a 2nd hand Infinity with the NAVI, for the same money you might just want to pickup a brand new "modern" Stereo, that'll have all that wireless functionality built in, plus offer much more besides (greater Specs plus features).