Re: Advice for a newbie!
The very first thing you need to do is to buy a repair manual.
The Clymer Force repair manual is about the best for your motor.
About the fuel water separator, if it is a normal one, yes, that is all there is to it.
If it is a Racor type with the clear bottom and a drain valve, you can usually get by with just draining what is in the cup.
Gear oil - lower unit gear lube for marine use, any one that is NOT labeled as "type C". You will need 23 ounces of lube for that gearcase, so pick up a quart, and get one of those $7 pumps that fit onto the top of the bottle to pump it into the gearcase.
For grease, a marine grade grease, many brands to choose from, each has its own name. Some guys swear by one brand over another. Some guys subscribe to the "any grease is better than no grease" motto, and use whatever they have in the grease gun. Since you are in Gulfport area, you will probably be venturing into saltwater, so get a good marine grade grease.
You should be able to get these items at any marine shop.