the only real way to find out where it's leaking from is to smoke test. but if you choose not to then after you replace what ever you think it might be. drive it around, then take the gas off. when you ntake the gas cap off you should hear vaper pressor. if you don't hear any thing, you didn't fix the problem.
if you need help, or don't understand, PM with and I'll call you. I'm a smog tech.