A lot of these powerbook g4's have a small scratch line or detaching just above dvd drive. Its best to pull back that slightly left center clip properly to avoid damage to the case.
I just replaced the logic board in a 15-inch Powerbook. I usually grab heavy card stock and fold some packing tape over and stick it down stick side up. That way, I can stick the screws down in the order and arrangement they were removed. The fiddly little hook that secures the front of the palmrest above the Superdrive slot is a bear to remove though. Be patient with that one. I also didn't reconnect the optical drive cable correctly and I'm reluctant to open it back up to fix it. Take your time.
They're not bad, they just take patience. If you have ice cube trays or an egg carton you can use them to hold the screws. Marking where they went isn't a bad idea either.