Your light requirements are really going to be dictated by what you plan to put in the tank. With a fish-only system, or fish-only w/live rock, your light needs are not that big. With inverts your requirements will go up, in some cases way up. What are you planning to house in it?
As far as other equipment, I would suggest looking into a small protein skimmer which is something that you wouldn't have already if making the swithch from freshwater. Liverock can serve as the majority of your filtration. Lots of good info on that available here. I would also pick up a good reference book. My suggestion is the Conscientious Marine Aquarist by Robert Fenner. That will give you a fairly good idea on how to proceed.
Good luck with the new tank