As a member of the Good Sam Club which runs about $25 you get 10% discounts at Good Sam parks and usually they are the better parks even though some are priced nicely.
As a member you can run online your trip. It will show gas stations on the way, miles and expected cost for gas based on today's prices. Diesel cost more now than reg. gas, but drives better in mountainous areas. Eating in is a plus, campground rates go from free, to $25. on up to high as you can imagine for fancy resorts. There used to be terrible tales of the roads to Alaska and how it tore up rv tires. Check with rv rental co. to see what their cost are and if they handle any vehicle damage. I see a link on this page to www.campetravelusa.com Not familiar with this site, but might be helpful to you.