First TT Trip... in freezing temps advice please!

If you are going to be below freezing for the entire trip I would not de-winterize. Do not use the FW tank or plumbing at all. Use bottled water for everything and do not dump into the holding tanks. Take "back packing" baths (heat a little water and just wash off).

If you try to use the on board plumbing (shower, toilet, etc.) you will likely run into freezing up. Don't risk it.