Welcome to the forum . . . and greetings to Brooklin, Maine! I attended Wooden Boat School there in the early 90's, and camped in our old 25' AS right there on the water by the shop.
FYI there is a 20-footer thread, where you can get specific advice for our model:
There is also a Sticky Topic on winterizing in the Winterizing sub-forum, so for rough guidelines just go backwards in the process:
Don't forget to flush out all the lines, incl. water heater, with good clean city water using an inline water filter, and new hose for potable water.
You should also treat the water tank, pump, and water lines with a dilute bleach solution, and then flush them out well with city water:
PS -- and the owner's manual, as just suggested.