Shouldn't be a problem - how fast is your iBook? 800Mhz G4 or better with 512 ram should be fine. You will need to download a DVD playing program to watch the movies as well, as Apple's DVD player app is probably not installed on your system.
So what drive to get? Get an external firewire drive that can write DVD's - doesn't have to be able to write dual layer, as long as it can read regular DVD's. That way after spending money on the thing, it can also serve as a way to backup your stuff.