How Can I Update My Map Software For My Garmin Gps System?
If you are talking about the road data, you want City Navigator NT. There are a couple of options. You can check with Garmin to see if you are eligible for free map updates at https://my.garmin.com/maps/updates.htm
If you are not, they will point you toward the download, DVD, or SD/microSD card versions of City Navigator NT. The update costs between $70-100.
You may want to check out EdgeGPS.com. They are an authorized Garmin Dealer that can get you the map software you want at an affordable price. Their customer service is outstanding!