US95 between Yuma and Vegas is really fairly flat. There may be some increase in elevation, but no real grades or passes. I usually stay on the east side of the river on AZ95 between I-10 and I-40. That section of US95 in CA was very rough the last time I was there. This may have been improved.
As to fuel stops, the total distance is a little over 300 miles. There should be fuel in any of the towns you pass through. Try to avoid buying fuel in Needles. Very high priced. Bullhead City, AZ usually has pretty good fuel prices and there is a Sam's Club there if you are members.
There should be no problems with this route. Stay safe!