About To Do It Questions
I am sure the earler posters meant well and were trying to give you some idea of the issues that might arise but...you really should have no problem. 35ft is large enough to have adequate ventilation and small enough to be serviced by a couple small cheap space heaters. The West Marine space heaters at $50 are no better than the $15 ones you can find at hardware stores. Best to get the better ceramic ones though for safety.
Condensation....a problem in FLA, but not in the Northeast. I kept my boat in the water through DEC into JAN, did nothing special and stayed aboard every weekend (got down to the 20''s here in MD). Never a problem....by and large because colder air IS much drier. Humidity is much much lower in the colder months in NE. Don''t sweat it. But....DO have good ventilation (my boat has two dorades and two mushroom vents ...and yes, I do need to close these when I want it warmer)...but...you could also keep the boat a relatively uniform temp and had no problems with humidity. Again...an electric space heater helps here as it produces no water vapor the way other fuel heaters can. And no CO to worry about.
As for boats being wet....there really is no reason why a boat should be wet, at the dock especially. I have had quite a few boats and the wet ones were the old cheap tired ones. A newer boat kept in GOOD condition (and that takes work....replacing old plumbing, making sure the keel bolts are secure and not leaking, installing a dripless shaft seal etc) should not have any water in it at all, not in the bilge not anywhere. It can be done.
SO, easy....keep a fan on low, just to move air around. Get two or three (if you want one for the head) cheap electric space heaters (but suggest you only use ONE specially protected ceramic one to keep on during the day). To be completely on the safe side...probably best to have all the space heaters be ceramic.
I also don''t think you should have a problem with the Dufour and insulation. Don''t bother unless you do. Your inner cabin must be lined with something on that boat...it is not just naked glass is it? I would not think so on that boat. Also...I am not sure...but Dufours of that vintage may be balsa cored...that will help also. Jeff H will know more about this.
And yes, keep your dress clothes in your car.
Don''t worry, lots of people are doing this with no problems. Its not a big deal.
Hope this helps