How much time do you have to research? One week is plenty if you can dedicate 3 - 4 hours, or more a day on it. Word to the wise, diving gear is Life Support Equipment. With that in mind, nothing that is going to support your life (BC, reg), should be purchased used, unless 1- you know the seller, and 2- you have time to have the gear properly inspected and signed off, which you do not. To purchase items which require checking the fit over the internet is not always a good choice, unless you've tried the item at a local LDS and are merely shopping for the lowest price. Be careful of Leisure Pro; they are NOT an authorized dealer of the products they sell, so you will not have manufacturer's warranty on items purchased from them (not a good thing to forego on regulators and bc's). They will offer you their own warranty, but it will not be the same, plus if something requires warranty service, you have to send the item to them and be subject to their timetable in getting the item back to you.
Do check with scubatoys and get their advise. Depending on how fancy or how practical you want to get, you can pick up a brand new regulator, octo, console and bc package for about what you have to spend, give or take a few bucks.
Have a nice trip; Maui is great for diving!