A good MCAT score?

A 10 or better in all three sections.

A composite score of 30 is competitive. More balanced scores are better than "lop-sided." E.g. 10, 10,10 is better than 13, 13, 4.

If you just need a content review and not a formal class, I would recommend taking a look at http://www.FreeMCATPrep.com - they have an outline that is modeled after AAMC's (the testmaker) topic lists. Also, they have a bunch of practice questions so you can gauge where you are (and it's 100% free, unlike those other expensive companies).

Good luck with your preparation!