Fixing an aging Tiger Provan

Tigers used to be the shznit!  Kinda the start of light duty commercially built overlanding or expedition rigs iirc. 
Your question is very open ended though, with an aire of “Have no idea what to do or where to start”

Based on this, Be careful you don’t just remove a bunch of stuff and end up with a gutted pile of junk. 
Also at that age, do you know or are you assuming the clam shell is well sealed and there’s no damage or water damage there or in the floor?  
And you need to decide what you want to do. Cosmetic stuff like flooring and upholstery or more comprehensive like replacing appliances and utilities.