If you have a lot of tracks or routes stored in the .gpx file, it is best to go down a level and highlight just the waypoints for display in Google Earth. If you highlight the whole .gpx file, it can take Google Earth a LONG time to load and display your data.
You should have a Google Earth icon in the Humminbird tool bar that turns blue when you select either a .gpx file or its waypoints, tracks, or routes. You can click that icon instead of using the right mouse button in order to display the selected data in Google Earth.
Editing a file name is done in Humminbird PC, not in Google Earth. Just put your cursor in the name field of an existing waypoint and type in a new name.