About a year ago I restored the roof on our 1996 Southwind. A lot of the white coating had worn off.
I washed it with Tide Powder Detergent and allowed it to dry.
Eternabond was applied along the roof edges. (I previously applied it to the seams)
Then I coated the roof with two light coats of Heng's Rubber Roof Coating. NO primer is needed.
It looks good and is leak free.
The Tide powder was recommended by Heng's.
I bought 3 gallons of Heng's and had half a gallon left when the project was finished.
Our Southwind is 37' long but, the actually roof is 30'.
It's not difficult. I used scaffold for working along the roof edge.
The scaffold is easier than a ladder, but a ladder will get the job done.
I would definitely try to coat the roof before replacing it.