Answer to: Wifi (in grey) could not be turned on?Definitely hardware. If it is in warranty and no other issues Apple will replace it. Don't forget to backup first.
Answer to: How do I eject a disk?Assuming you are on a macbook air. One way is to go into finder and under FINDER in menu bar click on preferences. Click on sidebar button at top of pop up window. Bottom of list is devices, check the box for show cds, dvds on desktop. Go to the desktop and control click (right click ) on the cd/dvd icon and choose eject. You can also drag the cd/dvd icon to the trash can which will turn into an eject button.