A clean install of 9.anything should automagically update to 9.2.2 after a few rounds of Software Update/reboot/Software Update. IDK id SU is included with 8.6, but it won't update you to 9.x anyway. 9 was a paid upgrade.

Look in Control Panels for Software Update.

IMHO the best thing you can do with that machine is upgrade the RAM as much as you can afford and install OS X 10.3. Also investigate overclocking the CPU and/or picking up a cheap faster G3 ZIF from IC-China on ebay.