Mike,
Either method should work, sheeting, or the foam and fiberglass. Which would you rather do, or find easier to do? I'd have to do the sheeting/cutting, fiberglass doesn't like me at all (allergic to it).
Can you build from pictures? Yes, may not be the most accurate depending on perspective (pun intended).
If you have access to the boat then you have it made! Make every measurement known to man of the thing. Then draw it up converting those measurements to whatever scale you want. That ought'a keep you busy for at least an hour or two (for the next month or so, maybe). Also might give you an idea of why there aren't kits of every boat ever made, too much work.
All joking aside, it's certainly possible and lots of people have done it (not me, I'm way too lazy!).
- 'Doc