Just take it? Study? What to do...

I took Practice Test #1 from GMATPrep last night, as a diagnostic, and felt like I was reading Hebrew for a number of questions on the Quantitative section (I've taken Hebrew, years ago, so it was vaguely familiar, but I had no idea what any of it meant). I graduated from undergrad nine years ago, haven't taken a math class since 1997, so I guess that makes sense. But I didn't feel completely clueless on everything. Verbal was also a stretch, but I felt more confident and on the ones I felt were over my head, I was able to narrow it down to two or three, and then just went with my gut. Long story short, I didn't feel terribly comfortable with it, but my score was a 740, Q47/V45.

I'm not trying to get into a major school. I don't have the means to go full time, and would rather do a part time program at a local university (Eastern Michigan) while continuing to work. Plus while I have a strong undergrad career (albeit in History), I had a horrible year of grad school right after my undergrad and figure that I won't be able to get in anywhere decent with that record anyway. But I digress. Eastern pretty much just requires a 500 on the GMAT to get into the program in which I would like to enroll.

So... if you were in my shoes, would you feel comfortable just taking the GMAT with no further prep, if your diagnostic test was a 740 and you're not looking to get into a tier one school? I was prepared to spend at least two or three months boning up on things, but now I'm worried it may be a waste of time (like it was with my SATs - took the PSAT, got xxxx, took the SAT without prep, got same score, wasn't happy and prepped for another two months... same score a third time).

Any thoughts would be appreciated. I have no idea what I'm doing here.