Good luck on your purchase, and welcome to the forum. I also purchased a used RV that was sitting near the ocean and had been for a while. Bought it from down in Comifornia, and towed it home. There are going to be a number of things that I would be concerned about checking, and/or replacing before you move it far.
My first concern would be the bearings, seals, and brakes. I don't know how often, or ever, the previous owner did this, so check and make sure. You are sure to find some issues to deal with there. Another problem I have found with seldom used RV's is the valves. Toilet and black/gray tank drains mainly, they can dry up and leak, or stick from lack of use. The tires, if they are original '08 they need to be replaced, 5 years max for me, look for weather checking or any other issues. Some say if there is just weather cracks on the outside they are fine, I have found this not to be the case, just my experience. Then the bug issue, any ants or other critters make nests in the hidden areas? Then you have the other items you mentioned, all need addressing, but some can wait a little longer than others. The vents on the roof, covers for all the pipes, windows that don't leak, all important. If you blow a bearing or tire getting it home, not so much. Again, just my experience. Hope this helps a little.
As for places to shop? I have used many different ones, mostly Amazon, Dyers, and the ubiquitous Camping World.
RV Supplies, RV Accessories, RV Parts, Camper Parts, 5th Wheel Hitch
I am sure others will give opinions as well, some good experience here on the forum, use it.