sexyfishers, I'll help you with what I know so far (and don't worry, you are not imposing at all, it's how we all learn here).
I would have waited on the starfish, they need a very established tank or they will starve. Usually you need to wait at least 6 months, but some say 8-12 is better. The sump/refuge helps in many ways. It adds more water volume to your tank, and is where you can stick items that you don't want seen in your display tank. Like the cheato (macroalgea), it's very beneficial in keeping nitrates down and is a breading area for pods. It also steals nutrients out of the water that the bad algea likes to feed off of. You don't want it in your DT though or it will take over. I have hermits in my fuge because they are good scavengers (will eat anything) but I don't want them in my DT because I want my snail population to stay up (hermits will go after their shells). The fuge light I run at night, when the DT light is off. The cheato needs the light to grow and having at least one light on all the time helps keep your pH level.
The live rock works as an added filtration system and is home to many good organisms. Unlike my freshwater tank, I won't have to take out my decor and clean it.
Though I will turn a powerhead on it every once in a while to blow off any debris.
I'm still learning though, and have a ways to go, but I'm having fun. Good luck to you and your tank. Have you posted pics of your tank? If so, I'll hunt around to find them.