Jayson, getting to the internal drive of an eMac is a pain in the butt. That stuff is packed in there like a Chinese jigsaw puzzle. I really suggest you have a professional replace the drive if that is the route you want to take.
My suggestion is external, forget USB, the eMac only has USB 1.1, not USB 2 and Firewire is faster than USB 2 anyway.
I have several externals and the best ones come from a place called Other World Computing
, they have everything you need and pros who can help you figure out what you need. One of the coolest units they have is the Guardian Maximus
, it's a stand alone mirror RAID system.... I highly recommend them for backup security.