For someplace exotic, then booking through a TA (and usually paying EXTRA, which the OP was asking about saving money), can be helpful, if you're not familiar with the area. For SXM, it's really not that hard, to know what your options are for flights, etc. And for flights, travel agents have zero pull with anyone any more, like they used to have, years and years ago. For hotels, yeah, maybe. Flights, no.

The best two things that you can do to hopefully ensure less problems is to a) book a nonstop flight, if available and b) ALWAYS, ALWAYS, ALWAYS book directly with the airline, not through a booking agent like Expedia, Travelocity, etc. If there does happen to be a problem, the airline and the booking agent will chase each other around, each blaming the other for the problem, and leaving the passenger hanging..