Welcome to MobileRead, macarong!
I have a 700, too, and love it! I've actually never used the mp-3 player for the same reason as Elsi, I don't like music playing when I'm reading. It's too distracting.
If you have any questions about your reader, check the Sony forums first before you call the company. Many of us have had similar problems and the solutions are documented there. Good luck with your ereading!
Enjoy!