Setting up a 8 gallon tank with 2 clown fish

Hi, :)

I am new here and interested in getting a salt water tank with only 2 clown fish. I have been to my local fish shop. They had a start up kit including tank(filter/heater), two clown fish, sand, rock and water for 190.

I have gold fish tank(54 Litre) since I was a child and the oldest goldfish I have is 14 yrs old.

I want to find out the basics of does and dont's. example do I need a clean up crew for this size tank, what do I really need in setting up a salt water tank, what type of flakes / pellets or something compeletly defferent.

My LFS was saying with him giving me the sand the live rock and also the water he said I could put in the fish right away is this true.

Do I have to put in real coral or can I put in the fake stuff for decoration.

Thanks in advance.