I must be missing something. It seems like the ~$75 you would have to pay Garmin to buy City Navigator and then use it in BaseCamp or Mapsource would be well worth the money given the difficulty and frustrations people are encountering trying to get this job done in Google Maps.
I have been using it for years. I have given up trying to navigate off-pavement with routes. I convert the routes to tracks and use those for navigation.