SandyUT not a problem at all!
You should be missing the worst of the wet season in November. We tend to get most of our rain in Dec - May and then during the summer when hurricanes or storms come through. We just got a bunch of rain yesterday when tropical storm Bertha came right over us, but before that it hadn't rained in a while. Even when it does rain here, it usually only lasts a few minutes and then blows over. Constant rain for an hour or more is extremely rare.
Water temp was almost exactly 80 degrees (at a depth of ~100 ft) in November last year. I'm right across the channel from Grand Turk on South so we have nearly identical conditions... but the coldest I've seen in Grand Turk was ~78 at depth in January. I'm usually very comfortable doing multiple dives in a full 3 mm in the winter but I have a few coworkers who wear a hooded vest in addition to that. We occasionally have people wearing a full 5 mm in the spring but most of them seem to think that it's overkill.
You will probably fly interCarribean Airways (Air TCI) from Provo to GT (There is one other smaller carrier that only does a few flights, but I have never used them). With interCarribean Air, for each passenger, you get your first 50 lbs of checked baggage for free, regardless of whether it is in one bag or two. For each pound over 50, it's $0.50 per pound. You are technically also allowed two carry ons, but the plane is very small, so a standard overhead sized suitcase usually has to be checked. A backpack or a couple small bags on your lap is allowed. Depending on how full the plane is, I occasionally get away with carrying on my medium duffel bag too. They do require you to check in at least 45 minutes in advance or they won't let you on the flight. They are quite strict about that... Other then that interCarribean Airways is quite good! They sometimes run behind schedule in the morning, but are usually right on schedule by lunch and are very easy to use. The check-in/security in Provo is separate from that for the international flights, making it even easier after you have come through customs.
Finding a liquor store in GT is somewhat of an adventure... There is one that is fairly consistently open that I know of, but it's quite a walk from Bohio. Many of the stores in GT operate on a "when they feel like it" schedule. Almost nothing (except the hotel bars) will be open on Sunday. But yes, if you can find the liquor store, it will be much cheaper then the bars. Expect to pay ~$5 per bottled beer at a bar and more for mixed drinks or wine (Bohio is on the more expensive end). Your best bet might be duty free actually... You are allowed 1 liter of spirits or 2 liters of wine per person through customs with no duty...
