I've replaced numerous CD/DVD drives. Most are made pretty cheaply. There is a very small hole in the front of the drive and if you unbend a paperclip, you can push it into the hole and hit the mechanism to open the drive to retrieve a disk stuck inside. But as far as it not opening anymore....sounds like it needs replacing.
Mybe the mechanic part of the drive went kaput. Or somehow the drive plate is stuck because of a loose part inside. If you find out what the problem is you may be able to fix it. Although, i think you should consider buying a new drive.