Re: topsail island
I have sailed there quite a bit with a Precision 18, which is very similar to your description of your boat in many ways. The channel that runs inland along the island is rather narrow for sailing, but maybe not as bad as you might think because the sea breeze tends to be perpendicular to it, so you are broad reaching most of the time. For me the attraction was getting out to the ocean and how feasible that is depends on where you are on the island. If you are somewhere in the middle, it is probably not worth it. If you are closer to either end, then the dock at your rental is a real asset.
Unless the surf is really high, one can get out to the ocean both at New River Inlet in the N and Topsail Inlet in the S. You have to be careful though. Watch the forecast and don't get caught outside with building seas. The channel can move so it is not charted in detail but it is dredged and marked well. Often waves will be breaking on either side of the channel, so coming in you have to make sure that you stay in the channel. The first few times in and out it can be very exciting. Once you are more comfortable, other things can be added such as trolling a spinner. Fishing is not bad there, so that might be another reason to take the boat.
The boat ramp on Topsail Island is a bit S of the town of Topsail Beach, so it is much more convenient for the S end of the island. The ramp is rather shallow there. I had to uncouple the trailer from the hitch and let it out on a line some 6-8 feet before I could float the boat off.
If you are close to the N end, New River Marina on Swan Point Rd has a boat ramp and they also might have reasonably priced transient docks if you want to keep the boat there. There are also a couple of ramps at Sneeds Ferry (Fulchard Landing and Old Ferry marina). They might also have transient slips. If the ocean is too rough, sailing in the New River would be an option very similar to lake sailing.
You might want to look the area over in Google Maps in satellite view to get a better feel for the place and see if there is enough for you to do with the boat.
One of the things you will see in Google Maps is that there are a lot of false leads in the shallow inland side of the island. If you follow your depth sounder into one of these, you can find yourself at a dead end and have to turn around and back out. Luckily the shoals don't seem to move much here, so you can use the satellite imagery as a rough guide.