SW is not that much different, if you are reading about sumps and fuges you are already on the right track. I learned most of my stuff readin online and through books. Really is easy, trust me. Until the tank gets mature and established there is a bit more cleaning and checking water parameters, but most of the parameters are the same thing you would check on FW. Now there are more to be concerned with but still same principle applies.
You will want to watch your PH, instead of a 7.0 in FW you will want 8.0+ on SW and then high you want it depends on if you keep corals or not. With my reef I'm at 8.4. Still test for amonia(sp?) then some new ones i do that i didn't do for FW is nitrite, nitrate, phosphate, calcium (big one for reefs) magnisium, and alkalinity. On top of this depending on what you keep you will want to certain specific gravity/salinity. Mine runs 1.025. You don't need an RO/DI system but it does make life a bit easier than toting jugs around. . Use the RO for top off and of course SW for water changes. The water does need to be RO or RO/DI water. Anything else, especailly around here is going to cause crazy algae bloom in the tank (thats not good for the reef tanks can choke out your corals) Now you will get all kinds of differnt blooms when you initally set up your tank, think i went through 3 or 4 different stages with mine.
As far as sump goes, i think its a must. Once again depending on what live stock you keep it will help, like thats where most people stick their protien skimmers (helps to pull bad stuff out of the water, you can kindda relate it to a canister filter but then again not so much)and hide the heaters/thermometers/auto top off and whatever else. The water circulation from there helps airate your water. The fuge will help keep a steady PH during the nite if you get some macroalgae in there, but its also a good breeding spot for all you pods that some fish depend on for food. If you don't have lots of these fish usually the LR and sand in the display will provide what you need.
This is just a scratch of what you can expect, theres more too it but i'd be typing all night to cover half of it. Its not hard to keep a SW tank, just a bit of good ol monitoring and the know how.. Oh let me state this while i'm thinking of it, invest in a lil tank for quarantine!!! This is a must, I didn't do it at first because i never had any issues with my freshys, but sick fish sure can reak havoc on your tank. Been there done that not gonna do it again. Lots of time money and aggervation to learn that lesson when i read it was a must and just disreguarded it..
Anyhow hope this helps some.