First off, Apple has an iBook extended replacement program for the logic board here:
Thus if you already think you have a hardware failure, and are out of your one year or AppleCare warranty you may still have a place to turn to from Apple. Check the above link for what conditions they will consider replacing your logic board.
Some tips I have for those who have yet to have problems with their iBook but want to take proactive steps to preventing needed repair problems:
1. Before moving, make sure all cables are disconnected.
2. Remove the cables using the bulb connector and do not attempt to pull the cord itself. The bulb is as much for insulation as it is to make sure it gets pulled straight out instead of bending the ports. Since the ports are connected to the motherboard (logic board) breaking those ports will require replacing the motherboard. So be careful when disconnecting cables. Too frequently people rush to move their laptops and don't pay attention to resistence they get removing cables.
3. Don't let the power cable bend at the bulb. That area is easy to fray and is a weakness of almost all laptop computers.
4. The power connector that plugs into the laptop has a silver colored din which can be covered by the plastic cap they came with. Try not to lose the clear plastic cap. It will protect the power connector from accidental damage in the bag.
5. Note, don't pack the laptop in a bag with many loose crumbs, broken lead pencil tips, or anything else which might end up in the keyboard.
6. Don't eat or drink near the computer! Accidents will happen, and Apple does not cover coffee spilling into keyboards.
7. Carry the laptop with both hands. I dropped my 17" Powerbook when I tripped, and it cost me $800 since Apple does not cover user accidents.
8. Pack the laptop in a foam sealed case. Jarring movements are not good for laptops.
9. Shut down the computer before moving outside. The heads are only parked when you shut down and may get misaligned if they aren't parked when the computer is being moved.