Blacked out iMac screen. Any suggestions?

Can you boot from the Recovery HD? If not or if the screen blacks out, then make an appointment at the Apple Retail Store - Genius Bar and take it in for service. If you are not in the USA or cannot set up an appointment this way, then contact your local Apple Store directly.

If you are using Lion or later then the Recovery HD is on the Hard Disk Drive. You boot like this:

Boot Using Command+R keys:

1. Restart the computer.

2. Immediately after the chime press and hold down the

"COMMAND" and the "R" keys together.

3. Release the keys when the Utilities Menu appears.

As for the DVD:

Five ways to eject a stuck CD or DVD from the optical drive

Ejecting the stuck disc can usually be done in one of the following ways:

1. Restart the computer and after the chime press and hold down the

left mouse button until the disc ejects.

2. Press the Eject button on your keyboard.

3. Click on the Eject button in the menubar.

4. Press COMMAND-E.

5. If none of the above work try this: Open the Terminal application in

your Utilities folder. At the prompt enter or paste the following:

/usr/bin/drutil eject

If this fails then try this:

Boot the computer into Single-user Mode. At the prompt enter the same command as used above. To restart the computer enter "reboot" at the prompt without quotes.

If the black screen persists even booting from the Recovery HD, then most likely the drive is toast.