I feel your pain......and did extensive research on the internet.....Google "LX470, CD, err3" or "Nakamichi, CD, err3".
Take a look at this excellent explanation of how to dismantle and remove the head unit and retreive the jammed discs. I have used it and fished out three discs, but the CD Player still shows ERR3. An hour of work, so be prepared.
This is a site that provides repair services once you get the head unit out. http://www.carstereohelp.com/lexus.htm
"Six CD changer, Err message in display, will not play CD's, will not eject or accept CD's. Before repair, disconnect one of the car battery terminals for several minutes. This acts as a reset and may bring the changer back to working conditions. Otherwise, repair rate $385."
The Lexus dealer wants $750 to replace with a refurbished unit. Don't go down that route. Read these nightmare stories.
Don't buy a stray unit off of ebay, it is probably jammed or broken with the ERR3 meesage too!
If the home repair method doesn't work, then it will be better to just upgrade to a new head unit. I am buying a Jensen VM9215HD to get a multimedia system with all the trimmings and full iPod control for $460. Available on ebay or online stores. I'll install the unit myself, but you can get the unit and the job done at a local auto sound store for under $1000.
1999 LX470 97,500 miles, ERR3 CD player