cd rom broken--how to fix?

My cd rom no longer reads or writes anything. It began a few months ago, the writer started writing slower and slower, and the player began getting more and more confused and slow, until it completely stopped working all together. I had the school computer technician look at it for me and he said there was nothing that he could do and that I would probably need to get a completely new cd drive all together. how do I go about this in person? can I go BestBuy or someplace? or do I strictly need to make an appointment to have a dell person come to my house and fix it(becuase I DO NOT want to send it out) (I need my computer too desperately)?

Thank you so much for your help! ;)

Tanya