As others have said, stick to the OR coast. Work from north to south so you're on the ocean side of the road. Easier to get off at the scenic pull offs that way.
Some have suggested going without reservations, but as this is your first foray into the RV lifestyle, I'd get reservations to save stress on the road. The OR state parks are simply wonderful. Pick 3 or 4 and stay 2-3 nights at each.
Among our favorites: Harris Beach SP, Sunset Bay SP, Beachside SRA, Tillicum Beach CG (NFS). So many good options along the OR coast. Search here under Campgrounds for "Oregon" and you'll get lots of recommendations.
Check out
this brochure for info on some of the lighthouses along the coast. Interesting way to break up a drive along the coast.
As for the amount of time, the last time we went to OR, we spent two weeks just on the southern half of the OR coast.
