:it is 14 feet long 25 inches wide or so and has a totaly flat bottom.

I would try to find out what design it is and, If possible, take it for a paddle.

Whichever way you go you will be putting in quite a bit of your time, some money, and possibly trying your wife's patients to some extent as she becomes a kayak builder's widow. Ask yourself if the shape and intended use of the boat warrants the effort.

14 feet long 25 inches wide and A TOTALLY FLAT BOTTOM. Sounds a bit doubtful to me.

I don't want to put you off if you are keen though. You could use it as a practice run to get the feel of the art, then research and build your ideal kayak and use this one for a flowerpot or something.

It is a smallish boat. You would get away with a gallon or so of epoxy if you are careful and do not need to fillet in bulkheads or such other work requiring epoxy. If you are not near a supplier get more epoxy than you think you will need. You don't want to be left short half way through the job if you have to wait for deliveries.

Have fun

Etienne