Can I mount my single tap handle to the fiberglass tub surround if there is no precut holes for the set?and if so how would I go about doing so?

Yes and no. Yes you can cut a hole in the surround material so you can mount a mixing valve but you need room to work. You usually run your supply pipes,mount the valve and then cut you hole centered on the valve. Most valves will give you a template. Is you valve already there?