Due to variations between iBook G4 models, your modem may look slightly different from the picture. All of the following steps apply to either model.
Remove the two Phillips screws at the corners of the modem.
Lift the modem and modem shield from the bottom.
Disconnect the RJ-11 cable from the top of the modem.
When replacing the modem, seat the shield first, and then connect the modem and press it firmly into the shield, making sure that it is connected to the logic board.
You have successfully removed the Modem. To reassemble your laptop, simply follow the directions in reverse order.