I wont say I'm a pro, but I do a lot of stuff myself. It sounds as if your boat is not in the water yet.
First thing, most places will change oil, filter and drive gear oil prior to the winter. This removes any possibility of water, freezing, etc. So, if you can find out if any of this work was done prior to winter, you'll save yourself a lot of time, money and work. If not, then here are a couple of sites that give some good information:
When it comes to the cabin, water systems, a/c, etc. Its not much to it. First, find your water heater and see if there is bypass hose. The bypass hose is used in the winterization to empty out the water heater first, the bypass it, so when filling the water system with the pink antifreeze, you dont wind up putting a lot of antifreeze in an empty water heater. If there is no bypass, then time to turn on the water. Either you have a water tank, a water supply inlet from shore or both. Start with the water tank. You should have a water pump switch someplace in your boat. On my 3200, its in the galley, next to the fridge. Turn it on, it will pressurize your water system. You should hear a pump working. The pump should stop after a few seconds. If it continues to pump, you have a leak someplace, time to figure that out. If not, turn on your main faucets, if you see pink stuff coming out, thats good. After a while, it will empty. Stop the pump. Fill your water tank, and repeat, purging out all antifreeze from both hot and cold faucets, showers, transom shower, outside faucet, etc. Once you do that, if you have a shore water supply, turn off the pump switch, hook up a garden hose to the supply inlet, and again drain out all your faucets. Marine stores sell some water tank tabs for cleaning it out, check with them, it gets rid of a lot of smells.
Thinks like the a/c pull water from under the boat, so unless you can rig something to do your a/c, this can be done once its in the water. Do check your shut off valves first, before it goes in the water. Once in the water, the a/c can be purge of any antifreeze simply by running it.
Cleaning the boat, hull, canvas, inside, outside, waxing, etc is all done easier when its still on land. Do as much of that before it goes in the water.
Engines and outdrives. Once you've checked/done oil/filter/gear lube, fuel filter/seperator, time to hook up muffs and start each motor. If you're mechanically inclined and know about engines, thats good. If not, find a buddy or another boat owner who can help. One guy watches the drive to make sure water is pumping out, another one has the head in the bilge to listen for noise, check for leaks, etc. Let each engine run for a while, check your temperature gauges. I check the temperature of the risers as well by actually touching them. They should be warm, not hot. If they are too hot to touch, you have an issue that should be checked by a mechanic. Once your engines are running, check for proper working of your outdrives, trim tabs, all lights, etc, anything electrical.
There is probably more to write, but this is a good start.