I'm not from that area of the country but this is their web site with requirements.
http://www.police.co.nassau.ny.us/recrui...
As you can see you need 32 semester hours of college. That is about the average for most police departments in the country. They would like you to have a bachelors in almost anything but the AA is good enough. You can get that level of education from your community colleges and any AP courses you take in high school.
I know that their pay is very good for the area. A lot of NYPD officers regularly move over to that county for the money and a chance to live somewhere cheaper were the schools are better.
You need to be in good shape. There are a lot of physical components to the academy and to being a cop in general.
When you apply they will give you the specific physical requirements, if any, to get on the job. That will give you time to train for those specifics. In general for most departments the hardest parts are that you have to run and 8 minute mile for at least 1.5 miles and have enough upper body strength to pull yourself over a 6 or 8 foot wall (no toe holds like a fence) in less then 30 seconds.
Can't tell you what police work is like because I would need more room than an encyclopedia.
For me it was the most wonderful public service job in the world.