Lexus Repair: Lexus Navi, 2002 lexus es300, message playback

Question
I just purchased a 2002 Lexus ES300 which has a Navi system. The screen shows "unable to read DVD". When I bought the car (from used car lot), I was told I'd just have to reprogram the navi. I am unfamiliar with navi system. I read the manual,found the DVD in the trunk, took it out, DVD looked ok, no scratches but I cleaned the DVD but the same message appears. I put the DVD in a regular DVD player, message "playback feature not available". I called Lexus. I was told it might have an internal malfunction which costs $2,000 to repair or DVD costs $300! Help! Do you have any idea what the problem is or what I can do to get the system working (outside spending another $2,000 on the cost of the car). ANY thoughts, suggestions welcome even if it's outside your area of expertise.  Thank you.  

Answer
UNFORTUNATELY THE PROBLEM DOES SEEM TO BE THE NAV ECU(PLAYER). I WOULD ADVISE YOU TO TAKE IT TO A LEXUS DEALERSHIP SERVICE DEPARTMENT AND HAVE THEM DIAGNOSE IT. THEM GO BACK TO THE USED CAR LOT TO SEE IF ANYTHING CAN BE DONE TO REMEDY THIS MATTER. I'VE SEEN THIS BEFORE.THE WAY I CONFIRM THIS IS BY TEMPORARILY REPLACING THE ECU WITH A KNOWN GOOD ONE AND INSTALLING YOU'RE DVD AND SEEING WHAT THE OUT COME IS. IF IT WORKS, THEN ITS THE ECU(PLAYER).
GOODLUCK