Production of your PowerBook ended April 2002, which means it is just over seven years old. Generally Apple models over seven years old are considered obsolete and the Genius Desk is not supposed to offer repairs for them. However unless Apple has formally declared your PB model obsolete they will still take it.
Even if they can't offer repair services for an obsolete model I have found the Geniuses around here willing to at least test and offer suggestions for obsolete Macs. The ones I have run into are generally pretty nice folks and they are all dedicated Mac users themselves.
As to the possibility of your moving up to a new MacBook or MacBook Pro, you may get whiplash of the brain the first time you turn it on; it will be so much faster and have so much more disk space than your G4 PowerBook. And when Snow Leopard (OS X 10.6) comes out it will get even faster.
If you should take your PB to the Genius Desk be sure and mention all the help you have received at FineTunedMac. Every little bit helps get the word out about our new site.
