I did my hailport myself when I bought the boat, which wasn't hard. It just requires a good clean surface, patience and the right technique. I used a highly diluted soapy water under the decal, which was to allow for some movement if a goof happened and to make removal of air bubbles easier. By measure and re-measuring, then taping the decal with a tape hinge
on top, its not bad at all. One other tip is to apply the decal as soon as possible (inside a couple of weeks), as the adhesive will begin to set on the backing and make it harder over time.
Unfortunately, we tried to find the online company that we ordered from several years ago and couldn't. I do remember that all vinyl is not created equal. UV protection is obviously important.
That said, while you can save money doing it yourself, it is not one of the more expensive things you might pay a pro to do. With all the draft designs, ordering, second guessing, measuring, standing and staring, asking wife to come check, etc, I probably had half to a full day invested in the hailport. For an extra hundred, I could have had that day back to go sailing. Your call.