I don't think the GRE is a make or break thing, but it does count. If I were you I would definitely retake it. I wouldn't focus as much on memorizing words, but i would instead learn how to approach each question type. It's impossible to learn all the words so you have to be able to use methods to answer the questions. There are good prep classes through Princeton Review or you can get a study guide and work on your own. What were your percentile rankings and what did you get on the analytical writing?