I still get a lot of hits about mending iPods (because I had to fix one once) - quick version, use a guitar plectrum to get inside the case. So I though I'd add an entry like it about an iMac.
So here's a picture of the new iMac 20 inch Aluminium Chassis version, released a few days ago. Okay, I know. the front is missing. Still, it looks pretty densely packed. My advice for dismantling... don't.