Omg Rascal, sorry to read this
Exactly same thing happened on my iMac, the logicboard died.
Can i ask you something?
You didn't tried to install Jaguar by any chance?
It's probably a stupid thought but...
Jaguar has problems on iMacs 350, 400 (DVSE's) which might crash their logicboards.
It can be solved if you first upgrade the firmware
I myself had to find out the hardway to, and apple never mentioned this when they first released Jaguar.
I just found out a month ago actually.
I really thought or reclaiming the money from Apple, but what's the use
Still, i know how it feels to be without computer and yes... i to thought of getting an pc since it's cheaper.
Soooo... euhm... well, try to hang in there ok.
I think the new logicboard IS worth it
Hope to talk to you again soon, on your own little iMac friend