So basicly, you'll have a very expensive steel floor with a concrete top on it. Have they quoted you a price for the steel yet, and did you have an oxygen bottle ready or was one provided for you by the engineer and vendor?
I've seen and worked on a lot of steel decks as well as plywood forms for decks, and have yet to see a deck that thick.
Corregated steel decks less than 1/16 thick are self supporting across 6 to 8 feet when concrete is poured on them, and wood forms are usually supported with form jacks till the concrete cures. 9/16 steel on a 30" span is absolutely overkill.