Its actually pretty unlikely anything was hacked..unlikely that anyone actually broke into any of your accounts..
they dont actaully need any access to your email account to send out these messages..all they need is your email address itself, and your name, which is very easy to get..the spam/scam email was "spoofed", so it *looks* like its coming from you..but if you hit reply on the scam message, it wont actually reply to your email address..it will go somewhere else..
I have been getting spam "from myself" for ages!
its not really from my yahoo mail account, but it looks like it is..
very common..happens all the time.