Welcome to the board lunch..
Its great to hear you have been doing the homework first before jumping in. Nothing good ever comes quickly in a marine tank. Im guessing you already knew that though from reading your post.
To answer some of your questions...
No you do not need a UV sterilizer. Some people swear by them but most including myself don't use them.
The function of a calcium reactor is to keep your calcium in the tank at a certain level to promote coral growth. Depending on what you want in your tank you can get away without a reactor either by dosing calcium ( I dose Liquid Reactor) or just simple waterchanges. They only become a nesseccity if you have a tank choke full of calcium sucking SPS corals..
Once you get the tank up and running if you can get a scoop of livesand from an established tank it will greatly speed up the process of turning your dead sand live.
Can't help you with a skimmer choice cause Ive never used a HOB skimmer. I will say to stay away from Seaclones though as they are more or less a waste of money from what Im hearing.
It would help if we knew what kind of corals you would like to start with, but Im thinking some zoos, xenia, colt, mushrooms, GSP would all do really well for you under your lights.
