We stayed at the Medora Campground, just outside the south entrance in Medora. It's OK, a little tight on the spacing. We were only there for a couple of nights, visiting TRNP on the way to Glacier. We only visited the South Unit, but thought it was beautiful. Got to see the wild horses. The Painted Canyon section was very nice at sunset.
To get to Glacier, we actually chose to stay on the interstate (94/90). Overnighted in Bozeman and then went on up through Missoula and the east side of Flathead Lake on 35 to Highway 2 over to West Glacier. Some might consider that the long way around, but our drivers just felt better staying on the interstate.