Hey Mike, slow down before you blow a gasket. If you already have a Garmin nav device just download the 60-day free trial of Streets&Trips 2010 and see if it works with yours. If you have any familiarity with Garmin devices you will know that there's not a big difference among them in how the stuff transfers to them. Especially not the Nuvis.
The biggest issue will be that some Nuvi models can't store any routes, some can only store a single route and some can store up to ten. All of them can store waypoints (Locations, Favorites, whatever).
One thing you need to know if you want to transfer directly to the device plugged into a USB port is that you also need a live internet connection to the PC. The direct transfer functionality doesn't actually exist in Streets&Trips. It's a function of one of Microsoft's online features.
Otherwise you can export to a GPX file and load the stuff onto the nav device that way.
Lots of ways to skin this cat.
...ken...