My first hand advice on vanagon buying is "buy the best, as you cannot
afford the rest".I also have to ask why the interior is bad. Did a mouse
eat it up while stored? Why was the van stored?

 High mileage? See above. Take a antifreeze tester with you when you
buy,and draw out a sample. If it is not about a 50/50 mix, suspect a head
gasket leak.