Hello, welcome to AA
As far as I know your skimmer should be good for your tank, I use to have the same one for a 55 gal
. and it worked just fine. Some people might tell you otherwise.
The amount of light should be good for some beginners coral. If you go to www.liveaquaria.com
and check their coral section there is a beginners pack. But I would hold on a long while before adding corals.
The sand, well, some people prefer deep beds, 3-4 inches. Some of us like it just 1/2 to 1 inch, it means less algae growth and less bottom cleaning. It really up to you, what you like. Some people like bare bottoms too. The only problem with that is that some inverts like their sand.
I have fiji live rock, I bought mine from liveaquaria and had to cure it for 2 weeks, so far so good. I've never bought any marine stuff from e-bay so I don't know about that. If you want hitchhikers, well, sometimes you get lucky and get urchins with your live rock, sometimes not a thing shows up. You'll have to buy those. Coralline eventually grows on the live rock providing everything is good in the tank.
To cycle the tank you should first place the rock on bare bottom, then add your substrate. Then go to the store an get 1 raw (not seasoned either of course) shrimp and dump it in there (that way you don't have to use live fish to cycle tank), the shrimp will start to decompose and ammonia levels will start to rise. You may want to start testing 1 a week or so. Eventually ammonia will read 0, then you test nitrite, when nitrite is 0 then start testing for nitrate, and this one you want to be less than 20ppm. After all this you can buy a couple of hardy fishes and see how it goes.
For water nothing works better than an RO
system, I bought mine from e-bay for $99 and it works wonders, plus it will save you lots of $$ in the long run.
Hope this helps, you can also get a book and get more details.
By the way, are you using a filter? or a sump?
It would be good to add a sump. There's an article here about sumps.
Well, good luck and let us know how it goes!!