Go here and select which machine you have: [[Family:PowerBook_G4_Titanium#familyNavigation]]
For a complete clean up, I would look at the logic board guide. I would take the logic board out, clean out the heat sink vents, reapply thermal paste, blow out the fans and run it for several more years. Observe ESD Protocols: http://www.ifixit.com/Answers/View/8497/Electrostatic+discharge+%28ESD%29+control