If you don't have Mapsource or PC software that can support viewing .gpx files, there are a couple of freeby options.
For web based viewing, you can go to the Online GPX Viewer
You can upload the .GPX file or point to the URL where it is located and it will display it for you using Google Maps.
If you are on your own PC you can download the free version of Google Earth
, which will now also work with Mapsource. From there, you can do a File>Open and it will display the info in the .gpx file on the map.
These utilities will display track logs and waypoints with no problem. Complex Garmin routes will be more like a "connect the dots" display.