I agree with Bmann, priming the oil system would be a good idea after so much time sitting. The only other thing I would be worried about is that old gas, or whatever it has turned into after sitting for 4 years. Not sure how much liquid it left in the tank, but I would siphon as much out as possible and refill the tank with fresh gas before even attempting to start it. Probably would not hurt to put in a bottle or two of gas treatment/injector cleaner as well.
Then just look over everything, check all the fluids, make sure no animals built nests anywhere and start her up. You will also need to recharge or even replace the battery, obviously. You can start it up at home with the hose attached, but don't let it run for more than about 3 min.
Once you have determined that it runs properly, and before you take it out for an extended trip I would replace all the fluids (oil and coolant) and spark plugs. Make sure all your electricals work, lube up all your cables, moving parts, etc., then hit the water and enjoy.
Post back and let us know how it goes. Fingers crossed everything goes well!