I use Panaqua on the lower west side of Manhattan to service my gear, 42nd and 9th.
The people there are always nice and knowledgeable. They have classes and organize trips.
Though when I was in Turks and Caicos the local instructors there didnt have great things to say about New York dive clubs. So I never booked with them.
Wherever you choose, I would do the classroom and pool dives here and get a referral and finish the class in Hawaii. It is a very common way of getting instruction. If you dont you may end up diving somewhere better left to experienced divers. Like some dark cold quarry or off a beach in tidal surge.
i highly suggest getting you mask fins and snorkel in NYC, there are discount SCUBA stores in NYC if you dont mind a little hassle.