If you're a recruitable athlete, talk to coaches at the prep schools you're interested in. The main purpose of the PG year is for athletes who would like another year to mature before college. Also, if you're able to pay full freight, that would help. If you're good enough now to be recruited by some low D1 schools, after a PG year you'll be recruited by some of the better D1 schools.
Judging from your profile, you seem like you'll have an excellent chance at getting into prep school for PG year. The logistics of a PG year are like the logistics of applying to a college. You should start applying now, and you'll find out in the spring if you get in. If you choose to go, you'll begin next September and end at the end of the regular academic year.
Personally, I would advise you to do the PG option. First of all, many really prestigious colleges recruit at prep schools, and they love to recruit PGs. Assuming you're recruitable by any D1 school, and you're able to pay full tuition, you can literally pick any college you want. The system is unfairly biased towards athletes, and you definitely should take advantage of that. Also, doing another year in high school can only help you academically and athletically. Your SAT score is gonna go way up, and you're academics will look more impressive coming from a prep school.