There are videos and lists if you do a search. However:
When the oil is warm, suck out the oil with a vacuum extractor, suck out the transmission oil. Replace the transmission oil with the same volume of the recommended fluid. Replace the oil filter after adding some fresh oil to the new filter. This can all be done when you still are going to put a few hours on the boat. You want to run the new oil so there is fresh oil on the bearings.
Add stabilizer to the fuel tank and fill it. Mercruiser has a technique to add a fogging agent to the fuel when you last run the engine. It's a pain but the best solution. You can spray fogging oil into the spark plug holes or if you are lazy just spray it into the throttle while the engine is running until it runs really rough then shut it off.
Remove the blue drain plugs. You'll probably boil your hands when you do this and drop a few of the plugs. I think you have eight. If you have a shower or heater you need to drain those well also. My stuff is set up to drain well but you can use a shop bac or air line to get any pools out. I just drive the trailer around corners and up and down hills to slosh out all the water. Put it all back together the next day. and loosen the belt tension. Run your ballast pumps briefly to clear water in them.
Make sure your boat, including under the seats and glove box, is really dry. Leave the hull plugs out and put them in a cup holder. You're done.