My Google search suggests this campground is on Mattole Rd that runs between Ferndale (a very worthwhile visit) and Petrolia. If this is the place, I've driven this road, north to south twice, but never in an RV. It's a slow, twisty drive in a car. But beautiful, isolated and remote. Well worth it. Were it me, and I wanted to be super cautious, as I often am, I'd park the rig in one of the private parks in the area, then day trip it in the tow vehicle. Not only will this give you an idea of the feasibility of the undertaking, but you could probably pay for a site and have it waiting for you.
As an aside, another great drive in the general area is over to Shelter Cove. Though there is a campground, I would never take an RV down that grade. As you start down, signs warn of past fatalities of RV'ers. Great fish and chips. But it has been over a decade.
Finally, please post what you find if you go there. Definitely a place I would love to spend more time at.