Wife and I did the Aquacat out of Nassau, and it was our first Blue-water experience. We both had about 30 dives under our weight belts going into it.
How comfortable are you with your Buoyancy? They did a shark dive based around a "chumsickle" so shark sighting there was pretty much guaranteed. I don't think that it was any more dangerous than just diving in itself. During our week there was one other shark sighted - a Hammerhead - and we only saw that on another diver's photo.
Since you'll be around real reefs, the biggest factor is to make sure that you're confortable with your buoyancy control. For us, it took a little bit of dialing in since our weighting was tuned for freshwater up to that point.
A liveaboard is a GREAT way to get a lot of diving in though, without having to deal with getting to and from a dive site every day.