Well the most important thing is to turn over the engine by hand. Derek didn't do that in the video because there was not enough room to maneuver, but in almost all other video's he made you'll see him do that first, and not for the reason those are petrol engines.
But remember, Diesels have far higher compression so turning the engine over takes some force but it shouldn't be necessary to strain your back. But as you say the engine has last been used in 2015 I'm not to worried especially as it also has been given fresh fluids. Diesels are tougher then petrol engines. Also hearing the RV was standing somewhat protected I think you could be a very lucky guy.
You saw how derek did it, just go the same way, but be gentle with her. Throwing parts at it without really knowing if it runs and moves can just be wasting money. Also make sure that you have "huffing gas" (starter fluid) with you, because if there are glowplugs in it and they don't function you are going to have a hell of a task starting it. Brake fluid (in a spray can) will do the same thing.
Good to hear the RV is given new tires, but standing still for 7 years will not be good for the quality of the tires. check them for dry rot and cracks.
What a project, good luck, keep us posted. And pictures... We love pictures
