Dead logic board in my PowerBook G4

My PowerBook G4 is dead, really dead. The technician said the logic board "suffered a failure," which somehow caused a secondary failure in the keyboard cable. He didn't offer a reason for this, and I was so stunned by the $1100+ repair costs I didn't to think to ask. I've seen in discussion boards for the iBook G4 that removing the bottom casing and placing some sort of shim in there can help because the pressure created when the housing is replaced can press the logic board against the graphics chip. Is that anything that would even be worth trying with my PowerBook? I'm in no way a technically inclined person, so I have no idea how similar or dissimilar the innards of these two different models might be. I know someone who will be more than willing to give this a try if anyone out there thinks it's worth it. I have no problem replacing the keyboard cable & keyboard, but first I need to know whether I'll have a working computer to connect them to!

Thanks to anyone who can help with this.