Check out
GPS Visualizer. It'll convert almost anything GPS-related into almost anything else GPS related. Among other things, I've used it to create a route on Google Maps, then export that to a KML file, and then use gps visualizer to turn it into a Garmin GPX file, which I then upload to my Garmin Dezl.
Took me a month or so to get the hang of Base Camp, and it's still not as intuitive for me as Delorme's Street Atlas, but it works. And I can still create a route in Street Atlas, and then use gps visualizer to turn it into a GPX file.
For the motorhome, I NEVER use the Garmin GPS to create a route - I always create it on the computer, one way or another, and then upload it.
al