My shop where I store my ATV flooded this weekend due to Hurricane Matthew. We had about 3′ of water than didnt recede for about 3 hours. Im currently in the process of draining all of the fluids and so far it doesnt appear water made it into anything. How sealed are these things?

I am going to have to replace the air filter and all of the fluids. Should I purchase everything from the dealer? Im new to ATVs and havent even done the first service yet. Only ridden it about 5 times since I purchased it. Should I take it to the dealer and have them do everything?