Wow, the condition is amazing! Great job finding this iMac. The iMac G4 is also my favorite Mac, I have a 15 inch 700MHz version. If you have chosen Leopard for your iMac (probably a good choice with a processor of that speed), I recommend you read the guide here:
http://ppcarchive.dyniform.net/tuning-a-g4-for-leopard.html
to speed up your iMac. I followed all of the steps on my iBook G4 1.33GHz and the speed got much faster. Another thing you could try is the Leopard Market, which is like an app store for PPC that I made. More details at
http://leopardmarket.eu5.org.
I hope you have a great experience with your iMac, and congratulations on finding it at such a great condition!