You don't need to lift up the keyboard. Turn your powerbook over and you'll see a tiny square plate in the centre. Take out the battery then unscrew this plate. Here you will find the 2 ram slots for your powerbook.
There are two clips on either side of the RAM thats on top. Pull the clips away from the RAM and the chip should pop up slightly, lift it up and it slides out at a 45 degree angle. Pop the new chip in making sure its firmly in and reverse the procedure.
I just installed a 1gb stick yesterday its dead easy.