That price is awfully high for a 13 year old bike with that many miles on it. Size & performance-wise the ZX7 wouldn't be a bad fit for you, but I would shop around a little more. You could buy a much newer ZX7, or a 2 or 3 year old 600 with far less miles for that price. I'd really recommend a 600 for your first bike - insurance & maintenance costs would be lower, and they are lighter, more manageable bikes that are easier to handle while you're learning the ropes.
You're likely to meet people who are going to tell you to get a bigger bike, but it's much better to work your way up as you gain knowledge & experience than try to start at the top, with possibly fatal results.
I'd pass on that ZX7, shop the classifieds and the net to get a good idea of what bikes are going for, save a little more money up while you're looking, and be ABSOLUTELY CERTAIN to buy yourself some protective gear (helmet, gloves, jacket are a must, bike-specific boots and pants aren't bad if your budget can stand it).
Good luck finding the right bike. Don't forget to post pics out here when you get it......and welcome to our world......