Just a thought on this camper renovation: Tally up what needs to replaced and consider buying a second used camper as a donor for parts if you find much of the appliances or infrastructure faulty. You may find that it is easier to save the the skin and build fresh structure from the dimensions of the original one. I can understand the sentimental value because I am dealing with a potential project of my own from my late FIL.
You will run up against weight limitations of a 1/2t truck quickly if you plan to add any modern amenities to the camper. You are better off finding a 1t with large enough cab for your family. It will also give you the capacity to tow something behind the camper in the future.