What about using Finder's Sidebar and clicking the little eject symbol on the right of the disk's name?
Or you can select the disk on your Desktop or in Finder and press CMD+E to eject it.
I have a G5 at work with the Eject Menu in the Menu bar, and it has the option of opening the Superdrive - Open Superdrive or so, it's in another language.
There is a hole on the front of the drive. It is very hard to see and I had to open the computer and slide the drive out. I put some white paint around the hole so I can see it by looking threw the little holes on the front of the computer next time