For some reason, the GS trip planner has flatly refused to load, no matter which browser I use. Finally gave up and subscribed to RV Trip Wizard, which does 1 and 2 of LeeOdell suggestions. One can also input the monies spent each day, fuel used, etc. As one moves along a projected route, campgrounds pop up, which are linked to reparkreviews.com. I quite like that program, even though not all the campgrounds we've found and used were there (or in the GPS).
I don't know if I can export to our RM/GS GPS. Haven't tried. But I can and do download to an Excel spreadsheet, which helps keep us on budget and on track. And when the RM/GS GPS goes crazy, as it's down several times on this months long trip, we still have the address handy to the next location.