G4 titanium-Yes, Aluminum 12" yes these models either have tabs like the iBook's, or the 12" you have to pop off 4 keys to get to the screws, and then theres 1 black screw under the ram door. the 15" and 17" are all one piece, because they are illuminated, so changing the keyboard is a little more difficult, as you have to remove the whole palmrest.
let me know what model and i can further explain, or you can check out http://ifixit.com and find a guide.