Models of this iBook with an internal Airport Extreme card commonly encounter startup or crashing problems due to intermittent connector contact between the Airport card and logic board. Your iBook may fail to boot (screen remains black) or may crash/freeze at random times, possibly with a kernel panic. See Airport Extreme installation instructions at iBook G4 14" 1.42 GHz AirPort Extreme Card Replacement, additional notes for step 30.
If fixing the common iBook G4 Airport card intermittent connector contact problem I recommend following this guide up to step 32 to remove the card (antenna still attached). Clean the connector contacts using a high-quality contact cleaner spray, then replace the card. When reattaching the metal bracket place a small piece of cardboard or other non-conductive shim material under the tab where it rests against the card to provide additional down force. You may not need a new Airport Extreme card at all.
You might not need to remove the entire DC-In board and cable. This is removed because the DC-In jack blocks the upper case from being lifted off. I just removed the screw and pushed the board slightly in when removing the upper case to provide clearance. You may want to tape the board loosely in place when the screw is out to prevent it from falling out.