you might want to change the lighting to power compact lights that would do fine for a 10 gall. corals dont do well with plain florecent lights. what kind of mechanical filter do you have?
as far as the sand and lr you want 1-1 1/2lbs of lr. and sand you could use a real fine grade sand to go with a shallow sand bed probably sd or a dry oolitic sand. fish you probably only want 1 or 2 small fish but no more than that. for corals leathers, mushrooms, and zenias are good for beginners. also any biological growth for your fw will not survive salt and the other way around so you'll have to start your water from the beginning
you might want to consider a protein skimmer, do some checking on that. some people go without them, other people wont run a tank w/o one
here is a good article to read before getting into salt it is something you should really read about and get as much info as you can. (books, forums, articles) dont jump into it because it is completely different than fw
<a href="http://home.gardenet.co.za/landman/Starting%20with%20Marines.htm" target="_blank">starting with marines</a>