No, you don't need a high school diploma. You can buy the A+ study guide at almost any reputable bookstore, and study to prepare for the test. You do have to go to a certified testing location to take the test. If I remember correctly, it cost me about $250.00 to take the test, but that was approx 8 years ago. It is a timed test for both hardware and software. You can also purchase practice tests from PrepLogic, they have a $49.00 practice test special going on at the moment, but there's no comparison to having that degree, even if you have to get a GED and then go to a local junior college.
Good luck......