Our maiden voyage in 2011 with our partially renovated 1966 Avion is documented here.
http://forums.woodalls.com/Index.cfm/fuseaction/thread/tid/25607121.cfmWe found that one of the best and cheapest things that helped us in sub freezing weather was "reflectix" insulation. It is sort of like foil backed bubble,wrap, but it works very well when placed over windows.
I also echo the others of recommending the Wave 3 cat heater. It will keep you warm and toasty down to near zero, depending on your insulation, but keep a vent cracked, and a carbon monoxide detector going if using thru the night.
With some careful prep, and a little ingenuity, you can have a great time regardless of the weather conditions! :-)
Good luck!
Garry in Alaska