Sigh. I love the iMac G4. Everything about it just frakkin' cool. That arm! My only regret is in not finding the 20" model... we just have the low-end 15" screen.
Last time I had mine out, it worked... I had tried to install Linux, but it's a pain in the butt since that model doesn't like to boot from a USB installer, IIRC.
You mentioned the disc tray wasn't ejecting - remember that you can reboot the system by force (Five second hold on power button; release; press once to startup, and then hold down the mouse until tray opens).
There are lots of resources online regarding the G4, including hacks and project builds. Some folks have turned them into lamps, installed PC guts
), etc. One of the larger challenges is driving the display, since it doesn't use a standard connector to the motherboard. I had hoped to tackle a project to stuff the guts of a MacMini or something in there, but it's one of those things I never got around to.
You should be able to find some PC-133 SDRAM (700mhz and 800mhz models) or PC2100U (1Ghz or 1.25Ghz models) to see if the system will respond with good memory. It tops out at 1 gig of memory (512mb in the user-accessible slot, another in the "technician-install" slot, which requires disassembly - and that's a whole kettle of fish, involving very exact reapplication of thermal paste!). CanadaRam
has RAM modules for this model.
Here's the place to go for all the specs: EveryMac.com / iMacG4