Optical disk couldn't be repaired. Dealer promised to make me an offer for the repair. After several weeks, when no offer came, I decided to check iFixit to see whether I could possibly do it myself.
iFixit instructions are excellent. Repair was a little bit delicate because of the small screws, but otherwise it went very well. When all was done I just had one tiny screw left over. The optical disk and the Mac seem to function just as well with one tiny screw missing.
Don't be scared. Open your Mac, but use care and follow the instructions.