Bill's comments are right on the money - I've chartered cat's from 38 - 50 ft; started with my only experience was a summer of sailing on a buddies 22 ft catalina and a summer on my own Hunter 31 - took out a Sunsail Lagoon 42 on my first ever bareboat.
If you want, get a skipper for a halfday (costs depending on company). I'd suggest not bothering - and playing around a mooring ball to get the feel for the boat. The only time you need to dock is the first time pulling out, and the last day pulling in - and they will come out and help if needed. Most companies want you to put the boat on the 't' dock instead of in a slip anyway.
Do the BVI first. It rates a 1 in difficulty for all categories (anchoring, sailing, navigation) etc - yet a 5 out of 5 for fun
Either way, do it - next time you'll know how easy it is.