I dive, and I'm glad that I took the time to get certified. Your basic class, which will get your a basic c-card good for a 60 foot dive is around $250 - $300, if I remember correctly. Any of the dive shops around offer classes. I got certified thru NAUI, and was required to do 12 hours of classroom work, and 12 hours of pool work. After that, you take a test, pass, and then do your certification dives at a quarry (or down in the caribbean if you go on vacation). After your certification dives, you get your ticket, and you can rent tanks, and dive on your own.
If you are thinking about getting certified, get your basic c-card, followed right away by your advanced diver certification, and then sign up for some of the other classes that are offered which are very useful for diving off of NJ. Some examples of other classes are rescue diver, wreck diving, wreck penetration, artifacts collecting, dry suit, etc. All good classes, and they help you get more comfortable under water.