As far as the engines are concerned you change the oil and fuel filters then fire them up and run non-toxic anti-freeze through the raw water side of the cooling system until it comes out the exhausts. I say engines because you have a generator and a main engine. I drain the raw water strainers after running the anti-freeze through them.

The water system is also pretty easy. I drain my tanks and water heater, disconnect the hose from the tanks to the water system pump and put the free end in a bucket of non-toxic anti-freeze. I then run the water system until antifreeze comes out each faucet. Note, that I take the water heater out of the system after draining it so it doesn't get filled with anti-freeze. I do not put anti-freeze in my tanks. I do the same for my washdown pump. If your AC system uses cooong water, you will have to do the same for it. Basically a pretty simple process.

For the head, I disconnect the intake hose and pump anti-freeze through the system. I generally put about a gallon through the head. The amount depends on the length of your hose run to the holding tank. For 1.5" hose you need one gallon for every 10 feet of hose.

Finally I open all seacocks and let them drain out for an hour or so then close everything except the cockpit drains