Well, most of the fridge is already there. You just need to disassemble, sandblast the metal and paint (if the paint is in poor condition), replace the insulation with closed-cell spray foam, replace the refrigeration system with a modern Freon-free system, reassemble and put new seals on.

An old fridge can be quite simple, structurally speaking. It’s in the 70s and 80s when fridges started getting compact, difficult to repair, and disposable.