Don't stress too much about it. Though it's always nice to make a nice job of it a remote hole is no where near as critical as, say a Tower mounting hole.
Use any decent quality hole saw (avg. size teeth is fine, nothing too fine is required). Drill in reverse first when cutting through the gel coat then forward slowly on a high torque setting to get through the glass. Mos timportant thing to check is that the remote/drill won't interfere with anything on the inside.
Always chamfer the edges of the hole to give a nice finish and reduce spider cracking should the area take an impact later in its life or be subject to flexing.
Sealant wise.. any decent quality (anti-mold is best) bathroom sealant will work just fine.
Reinforcement isn't required...
The first hole you drill in your boat is the worst.. once you've done it once its not an issue.