1.I can't recall what happened with my entrance scholarship and how it went with the whole Payment Agreement. If I can recall this correctly, I'm pretty sure it should be enabled. You can always call the Office of the Registrar to clear this up.
2. The payment doesn't happen till early September I believe? And in full depends on how you plan on paying the school. If you pay in full, it will be due right away up front. If you plan on doing installments, there should be a guide somewhere along the payment page located
here
3. Many people buy used books. This site has a buying/selling section that often advertises used text books. Do not feel hesitant to wait your first week though when it comes to buying text books. Different profs may sometimes use different packages (I recall their being 3 if not 4 packages last year for Math for example).