Won't be worth it. If you really need an old and incompatible G3, get a beige desktop or something. Those are going for around 60-80, and you'd be able to run OS X on it.
Your computer is not on the list of supported computers for OS X, and its not on the "unsupported" supported computers for XPostFacto, which would let you install OS X up to Jaguar on it, available here:
I think you're SOL on installing OS X on that computer, but you can pick up used PowerMacs for under $100 that are upgradeable and can run OS X up to Jaguar with XPostFacto at many places around the web. Check out http://owcomputing.com for a used 8500 if you really wanna go that route.