I find the Nav in my Grand Cherokee no more distracting than listening to my Ex nag me while I drove with her in the car, so you will probably be ok.
Also be sure to experiment with the volume so its not too loud but not so soft that you cant hear it when you are playing your Rock Music, ok ?
Is the screen big enough so you can clearly see the mapped streets, and things ? This also helps one know if the little Leprechaun in there is really accurate or maybe had too much Vicks Nyquil this morning.
All I can say about this Nav stuff is that mine took me to the absolute worst, scary, parts of El Paso, Texas; like right next to the big Fence between Texas and Mexico, and I was the only person there driving a really nice Black, Optiguarded Jeep, and everyone was wanting to make it theirs..
So, again, you have to kind of know where you are anyway if possible..
Good luck with this DC !
Dan F