Hi whollymoses,
GMAT skills do tend to 'fade' over time - so it's not surprising that you might have to re-learn certain concepts that you have not thought about much in 8 years. The GMAT has also gone through some note-worthy changes in that time, so you also have to train for a different overall 'format.' That all having been said, the content and patterns of the Exam are essentially the same - so since you scored 700 before, I think that you would have a good shot at doing so again.
For free math practice and help, I recommend that you set up an account at Khan Academy (
www.khanacademy.org). The site is completely free and makes the learning a bit more fun and 'game-like' (as opposed to the dry academic approach taken by most books). While the site is vast, you should limit your studies to basic Arithmetic, Algebra and Geometry. You might find it beneficial to invest a little time re-building those skills, then you can return to your GMAT studies. It's also worth noting that the Quant section of the GMAT is NOT a 'math test' - it's a 'critical thinking' test that requires lots of little calculations as you work through it. Training to 'see' the Exam in a strategic way is one of the keys to scoring at the highest level.
From your post, it's not clear how long you've been studding, so it would help if you could provide a bit more information on how you've been studying and your goals:
1) When did you begin your recent studies?
2) Have you taken any practice CATs/mocks yet? How have you scored on EACH of your CATs (including the Quant and Verbal Scaled Scores for EACH)?
3) When are you planning to take the GMAT?
4) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich