Once you decide on the map software your going to use, google around to find who might have a sale on it.
The software should last you a long time, as long as they don't move any major highways.
The newer subdivisions that are built on a daily basis won't be current after a year, but that is what mapquest is for. ;-)
Pick up a windshield mount and make sure you have a cigarette power cable and you will be set.
http://www.ram-mount.com/Set up a bunch of waypoints before hand and start doing a few GOTO's, with a few wrong turns and watch it reroute for you.
You can FIND new addresses with the GPS ,. but much nicer sitting down at home with some time to enter a few waypoints on computer then sync to
GPS.
Save waypoints into mapsource file into a new folder and then figure out how to manage waypoints later.
Yahoo forums are talking on how with current tracks/maps you can now due an overlay with current Google Earth.
Kind of nice to see walk in the woods from air.