Dangerous to you? Not really, as long as it's unplugged.
Dangerous to your machine? Quite possibly if you aren't careful or don't know what you're doing.
Before you go cracking open your machine, let's verify what iMac you have. You said first generation...that would make it a 7-8 year old
computer. Is that right?
If not, can you at least tell us the shape of it? There's a list of iMac models
here. You can find out your processor speed by clicking on the apple in the upper left corner of your screen and selecting "About This Mac." That will help you narrow down which machine you have.
Once we know which machine you have, we can better figure out how tough it will be for you to open it up.
Edit: Okay...looking through some of your old posts, I see mention of a 17-inch iMac G5. Is this the machine we're dealing with here? If so, it's actually pretty easy to take apart. There are instructions for accessing the CD/DVD drive in
this PDF. If you can get the drive out, you might be able to have success either shaking the disc out or trying to (CAREFULLY) poke around and see if you can get it out. But I really feel like this should be a last resort. It seems like you've tried pretty much everything I can think of already, so I'm not sure what else to try. Are you still under warranty, or perhaps AppleCare? It would be best if Apple could take care of this for you.