You can get water and dump inside the park. You should have no problems maneuvering your rig. 1st stop is potable water, then dump station.

Mather Campground has water and dump and showers available just before you enter Mather Campground. So you don't have to deal with the Campground rangers. Turn right where it says camper services. Laundry is there as well.

Depends on the time of year. If it before mid April, I could not find anywhere. Ten-x was closed. Mather campground water was down to fire hydrant system being broken. Love’s in Williams does not have Potable water. I could not find any in Flagstaff either. I was able to finally fill up in Kingman at Flying J on my way out. The area is at a high elevation, and gets cold weather, so many places do not have outdoor faucets or water vending machines.

You can get potable water at Ten X CG but not for your RV holding tank, only for portable containers

I dumped, filled with water and bought propane at the Grand Canyon Camper Village in Tusayan, which is about 5 miles closer to FR-688 than going all the way to the park. Dump and fill was $15. Propane is obviously by the gallon. No waiting and nice people in the office and at the propane fill. There is only one dump station, so there could be a line, but I did not have to wait and no one was waiting on me.

If filling the tanks, Mather. If filling drinking jugs, we refilled each day while at the park at their Sping Water walls.

Unknown about dumping, but I believe the Ten-X campground has water spigots.