If you buy a refurbished iMac from Apple, you can certainly get AppleCare, but I'm not sure what happens if you are buying from a third party.
I'm also interested in buying a pre-Intel iMac. I haven't heard of any inherent defects; just the opposite. I'm more wary of the Intel version, from what I am hearing.
ibook G3 Mac OS X (10.3) 160GB external memory