My 96 LS400 had the same problem. I had my stereo repair shop fix it for about $125. The dealer wanted to replace the entire deck for something like $750. My 99 LX470 had the in dash 6 disc player which stopped working, that repair was about $450 at the same shop.
If you have a good car audio shop, they can uauslly fix them, or know where to send the unit. You can also do a google search of fixing the lexus decks and do the removal and install yourself. I liked having my local shop warranty the repair and installation. The LS400 deck was a pain to take out. I watch him do it. The LX470 was amazingly simple.
George