First off, for the most active message board on scuba related stuff, go to www.scubadiving.com (Rodale’s scuba site), and go to their Diver to Diver forum. Do a search, and you will get lots of input on pretty much any piece of gear you are interested in.
That said, if you were to post this same question there, you will be inundated by varying responses. Which will provide you with good input, but will not lead you to any concensus whatsoever ! But it’s a starting point.
Next, since it sounds like you have not been diving in a while, I would highly recommend some sort of refresher. Some dive shops offer a simple “refresh” course to reacquaint you, or you could take the OW class over again.
After that I’d highly recommend the AOW (Advanced Open Water). Your OW technically limits you to depths of only 60 feet (if I recall). So for starters, the AOW will get you to 100. You’ll also learn some other good stuff (night diving and navigation, both of which may be useful for your new job). And is a good “extra refresher” for diving.
And depending on how confident you are in the water, I’d also highly recommend the Rescue Course. It’s a bit of a surprize, but you come away more confident about your own diving ability than anything else. It comes from being sure you can take care of yourself before even considering attempting to help someone else. It’s easily the best course I’ve taken (and will kick your butt !).
On to gear. If you’re ready to plunk down for a complete setup, that’s great. If you have to pick and choose the order in which you obtain gear, search on the Rodale’s site, and you’ll get every possible sequence, and reasons to back it up.
I am a recreational diver, and have been diving for 5 years or so. I can only tell you about my gear, and what recommendations I can give:
BC - I went with a SeaQuest Balance (weight integrated, back inflate). I love this BC. But fit is more important than anything. So be sure to try them on. I like the back inflate because the normal “vest style” tended to act like a “bladder compression” device 
I also like the weight integrated as it is one less step in gearing up.
Computer - I went with a Suunto Favor Air. Although if I were buying today, I would go with the Suunto Cobra. There are a lot of pros and cons to air integrated or not, but I personally like it and have no regrets. A lot of divers think Suunto’s are too conservative, but not only are they somewhat adjustable, I prefer being more conservative. Given the amount of time you’ll likely spend underwater for this job, I would definitely get a Nitrox ready computer.
Oh. And a computer is a must. I would never consider a job that involves diving and doing it with tables.
Regulator - I have a Mares (I think X16 or something like that), and I really like it. I have used other divers’ regs and it wasn’t until I tried others that I appreciated mine. I think it’s all a matter of what you get used to, but mine is one of the easiest to breathe off - even at depth.
Mask- I won a Cressi Big Eyes mask in our dive club raffle, and I really like it. Again, fit is more important. But if it works for you, I’d recommend it. I really like the greater field of view. Again, it’s not until you compare it to a regular mask that you really notice the difference.
I would guess/bet that the place you’re going to will have tanks and weights, so I wouldn’t bother buying your own. Or, wait until you get there to decide whether you really want/need them.
One thing that comes to mind is a safety sausage or some sort of signalling device. Again, given the amount of diving it sounds like you’ll be doing, you’ll want to be prepared for unexpected currents whisking you away.
That should get you started.
Where in the Carribean are you going ?