Replace DVD Burner

If you plan on doing it yourself visit www.ifixit.com for detailed instructions. However if you don't feel you are up to doing it yourself simply take the machine into your local Apple Store or AASP for service. If the machine is covered by AppleCare then call AppleCare as this repair would definitely be covered.

My 20 cents worth. Don't replace the internal drive! They are finicky and slow! You are better off buying a good quality external optical drive. They are much more versatile and accept a wider range of branded discs. It will also be cheaper and a lot less hassle.

Here is a short list of options to get you started: http://eshop.macsales.com/shop/firewire/optical-drives/