For years I ran large motor yachts, the majority of which had teak decks. If you are going to keep this boat to that standard, then the decks will require daily washing and periodic cleaning (monthly or as needed) with a 2 part kit; a cleaner and a brightener. Few in the industry cover the teak with anything beyond a good quality teak oil (again quite often, to maintain an even look to the teak); it is constantly cleaned. I don't believe there is a product out there which would give you a proper yacht quality finish without being pretty slippery from spilled drinks and food.
You should consider the immense project it would be to finish the exterior decks with a varnish like product. After sanding every bit of it to a glass finish, it must be bleached with oxalic acid (several times?) so all the wood is the same color. Sand, then coat (or two) w/ a clear wood sealer, and sand. Then apply the varnish or whatever, let dry and sand again. And repeat until you have a finish you can swim in (ten coats for "yacht" finish). Then the maintenance is pretty much the same as above, only it has to be dried or you get water spots.
Neither way water proofs the decks; you need to calk to do that, and that is much easier on the oiled decks for sure.
I wouldn't use a house hold deck sealer or the like; you can get a layer of mold between those products and the natural oils in the teak.
Interior is pretty much the same prep, but professionals use blowers to keep the dust at a minimum. Contact any floor refinisher in your area for the product they use and you'll be set. I actually found it much more cost efficient to have them do it; about $1200.00 to do the interior of a 50' center cockpit boat, but I was too cheap at the time. Stupid me!
Good luck; it looks like you've got a steady job for some time to come.
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