1) You said portability was nice. It is. That's a personal decision you'll have to make, based on your comings and goings, working habits, lifestyle, etc.
2) Not sure on the battery question. No one I know who owns a PowerBook or iBook has a second battery, for whatever that's worth.
3) Yes, a little door open on the bottom and you slide the RAM in. The little manual in the iBook walks you through this (with little line art illustrations). You're instructed to have the iBook off, unplugged AND the battery removed. The manual explains it all, but yes...it's very easy. Pretty much everything Apple ships right now features easy RAM installation.
