But none of the options (ethernet/network connection or Target Disk Mode) is available to me.
The more info I get, the less I understand.
As long as your current iMac G3 has a working FireWire port, FW target mode is a viable option with the FW400-800 adapter cable. And there are your thumb drives.
You have a point with the info being overwhelming and less than helpful, but as long as you don't have your new iMac to check for the things mentioned it's all hanging in a sort of vacuum. All I can suggest for now is to unpack your Mac when it arrives, start it up and follow whatever prompts you'll be presented with so you can play and get familiar with it. Remember that pretty much everything can be adjusted at a later time.
