not opened the sunday route yet,
and yes, all cb's in use now should have 40 channels. you'll be ok on 21!
All you need to do is save the gpx file onto your computer. Then open Memory Map and go to "import" You wont be able to see the file you have saved as its the wrong type so change the file type at the bottom from mmo (memory map file) to gpx and you should be able to see the file you have saved. Choose it and it should open.