The last section has been completed, eliminating the 12 hour ferry ride.
Might want to think long and hard before taking that trip in a large motor home. When I rode(motorcycle) it in 09 and 10, I don't think I saw a car or truck that didn't have a broken windshield. The Trans Lab "Highway" (really a two lane gravel road for a long way) was extremely rough in sections. They only campers I saw were 4wd pickups with either a small trailer or an in-bed camper. Gas was very expensive in places, don't know about diesel.
That said I do it again in a heartbeat. It's the last wilderness on the east coast Nd truly an amazing place.
You might look into doing a tour of Newfoundland. Almost as wild and the major roads are paved. (And a short ferry ride will get you to Labrador, so you can say you were there)
Dave