Welcome to the group, dariva.
There are both free versions of mapping programs as well as products offered for sale from several sources. Among the free applications are googlemaps and the native blackberry maps. See Stinsonddog's gps page, http://home.comcast.net/~tamsterra/O...kberry_GPS.htm
for much good info. Also see the gps subforum here if you haven't already done so.
In a nutshell, the gps (either internal or an external bluetooth gps puck) provides the position information for the mapping program. The mapping program downloads the map or map data and updates as you move (if you are using the gps). Check ahead of time to make sure the application covers the regions where you plan to be when using it. You must have a data plan. If you are using one of the free applications, you may pay additional data fees unless you are on an unlimited plan.
On the unlocking question, I don't know best answer. I'll leave that to others.