Just got done with that trip! Yes, 98 is an excellent 2 lane road. Judging by the traffic, it is a major RV artery, lots of Class A's and Fifths that made ours seem tiny on the route. Watch for the turn in Kayenta onto 98 - it's not that obvious, and we blew past and had to go back.
There's a time change from Monument Valley to Wahweep. We arrived an hour earlier than we planned, but the site was open, so they let us check in.
Wahweap is a great campground, facility wise. WiFi is typical campground - barely useable. Avoid the camp store, prices are sky high. Laundry is pretty good, especially the dryers that are relatively speedy.
2012 F150 Eco, 4x4, SCrew, Max Tow, HD Payload
2017 Grand Design Imagine 2670MK