Email account comprimised

First: I don't believe it was your email account that was compromised, it was your password. It should be changed ASAP. This won't stop what's already lost, but it will prevent any future access.
Second: My computer wasn't hacked, but a friend's was. It wasn't until I received an email from someone I recognized as been in my friend's address book, that I realized what had happened. It took me three months of forwarding each email (with full headers) to the internet provider (abuse@ *****.***) hosting the email distribution. The full header allowed the internet provider to trace the distribuyion source of the stolen info and shut it down.
Third: The only true defense that I would know is to establish a very secure (obscure) password, or preferrably, change it frequently.
Hope my experience helps.