I used to work for Sprint Tech support before I got laid off... Sprint Nav (TeleNav) on the SERO plan is NOT free, you will be charged $10 a month. If you were on the Everything Data Plan for $69.99 or the Simply Everything Plan for $99.99 then it would be free. I'm on the SERO plan, I don't even use Sprint Nav... I actually use Mapquest Navigator which you pay $50 a year for - it's a actually better IMO
http://wireless.mapquest.com/mapquest-navigator