So some of the advertised GPS navigators/handhelds say they come pre-loaded with US maps. What happens when you want to use it in nother country? Does the GPS automatically download the right maps when you switch it on and it realizes you're in Italy (for eg)? Or do you need to download the maps yourself? Is there an additional cost for the extra maps? is there a monthly/annual service plan you need to sign up for over and above the purchase of the unit?