How is it "not working"?
If it will take the disk in, the blue light goes on and the spinner at the top in the XMB starts spinning but the disk does not, then it's the usual PS3 fault.
The blue laser (which is used for initial disk detection as well as reading bluray disks) has failed. You need to replace either the entire mech (which is not hard at all) or replace the laser sled (which is mildly difficult). Both are possible if you take your time, label all of your screws and follow a video guide.
Both parts are available on ebay - search for ps3 laser. Of course, if the console is in warranty, use it first.
If you elect for replacing the laser sled, DO NOT touch the screws underneath the bottom of the sled runners. You'll see the ones I mean once you have it open - They are locked with threadlock. These are for initial alignment of the sled and are correct from the factory. If you move these, there is essentially no chance of realigning the rails without specialist equipment.