Welcome to the forums, Terrapin. You don't say if this is a new purchase, but I'll go under that assumption. I don't remember the title of the thread, but I remember running across some excellent advice on where to begin restoration when I first was looking for my Airstream. Start with your running gear, lights, brakes, all you need for towing and make sure those systems are working well. Safety first.
Then make sure your exterior is weathertight from leak sources like windows, A/C, vents, etc. I think belly pan, frame, floor integrity and tongue issues were next. Then address your systems like LPG, plumbing, electric. Repair/replace appliances. Then on to interior casework, finishes, soft goods, etc. Polishing and sealing the exterior was towards the end of the laundry list. I may have missed something, but that's a summary of what I remember.
I know polishing is what most want to do first. And it does give a real boost to your inspriation to see that shine.
Good luck and don't forget to post pictures.