If you have some important data that you don't want lose, as a precaution it might be a good idea to boot your iBook into target FireWire disk mode (hold t while the iBook is booting, while it is connected via FireWire to another Mac I think.)
The iBook should appear as a hard drive on the other Mac, and you can drag any important files you want to back up from the iBook to the other computer.
Good luck!