RE: "could anyone suggest other problems they may have come across". In a boat thats 27 years old, everything and anything in the boat could be a problem. What is not a problem depends on how good a jobs the original designer and builder did, and how conscientious and dilengent the owners have been over the years. You can and should not assume anything. The tanks being replaced is a good example - if you mean water tanks, that's an interesting one because they would rarely make a list of likely repairs. Your reference to 'glass decks' prapoobably means not-teak, a plus only in the sense that teak deacks swould cause an automatic toss-out.
Good luck on this, and the best way to make your own luck is through the services of an expert, demanding marine surveyor and an engine surveyor.