Dissembling the iBook G4 is a fairly involved process, and will take you quite a long time. Though, as long as follow the instructions and have all the right tools you should be fine. I suggest printing out and following the iFixit guide:
http://www.ifixit.com/
One particularly nice thing they provide is a "screw guide". I would recommend taping the screws to a copy of it as you go along. Then you know exactly where they all came from when you come to putting it back together! The sheer number of different sized screws in the iBook is staggering. Without some sort of way of keeping track of them you'd pretty hard pushed to get them all in the right place!
I'm not sure what might cause the screen to be unaligned like that, but I agree with heavymetal4god that it might be worth checking the hinges. The optical drive should be a fairly simple replacement though...
http://www.ifixit.com/
One particularly nice thing they provide is a "screw guide". I would recommend taping the screws to a copy of it as you go along. Then you know exactly where they all came from when you come to putting it back together! The sheer number of different sized screws in the iBook is staggering. Without some sort of way of keeping track of them you'd pretty hard pushed to get them all in the right place!
I'm not sure what might cause the screen to be unaligned like that, but I agree with heavymetal4god that it might be worth checking the hinges. The optical drive should be a fairly simple replacement though...