So I need help on:
1: I'm going to get a plastic bin and put my water in it- will my fish and plants survive while I switch out the fert and sand for black sand and fert.
I know nothing about plants yet, but I would expect your fish to be fine. Honestly though for the price of a plastic bin, I'd just pick up a spare 10g at wal-mart instead... then you could just set it up with your new substrate, then move the plants over (presumably you'll have to rip them all up anyways in order to change the substrate?), along with the filter and the fish. The only real reason to keep your water is if you're worried about the parameters of your tap being differen than those of your old water. I come from a non-planted background though, where the old water has nitrates that I'd just as soon not put in the new tank.
2:I know bacteria settles in gravel, so it say, and in filters. If I add beneficial bacteria will that help with the bacteria going away from my gravel
What kind of filter are you running? If it's a HOB style or something of that nature, I'd be inclined to just keep an eye on the parameters but not worry overmuch. If you're really worried you can take some of the old substrate and stick it in a permeable baggie (pantihose, filter media bag, whatever) and drop it either in your filter, or hang it near the outflow of your filter.
3: I REALLY love the look of the LED that sit on top with those lil brackets that are like $50 for a 10 gallon one.
Your money, your tank. I'd have a hard time dropping $50 for a light on my 10 gallon, but I'm cheap, have a wife and 2 kids (but only one salary) and other hobbies that also eat my spare change. I suspect we seldom regret getting what we really want, though, if the money is available.
-Rick (the armchair aquarist)