6. It's a cheap budget notebook - maybe 2-2.5 hours with maximum power management enabled.
7. No, but the parts/installation won't be covered by warranty unless purchased from Dell.
Be sure you know what this is - it's a cheap, throwaway budget notebook - it's neither built for performance, battery life -- or for the long haul. It's built to be a cheap, home use, throwaway after warranty system.
If that's not what you're looking for, buy a higher line model -- you won't be happy with the design compromises needed to keep the price as low as it is for this model. You're not going to find a high performance battery, metal hinges, etc. in a system at this price level.