Q: Initialization error [-70012]  Valid DVD drive not found

Does the drive make any noise during power up? You may have had a drive fail completely. One thing to do is check System Profiler and look at the ATA info under Hardware and see if it finds the drive. If it is not found there, the CPU is not seeing the drive and the drive may be kaput.

You should be able to find information on ifixit, like at

http://www.ifixit.com/Guide/Repair/Installing-PowerBook-G4-Titanium-DVI-Optical- Drive/100/1

to see how to get the optical out. There may be instructions on getting a disc out of a failed drive there, or you may have to do a Google search for instructions, as I know they are out there and relatively simple to handle.