This is what a Mark Levinson amp looks like as installed in my 2001 Lexus LS430. Apparently these amps are prone to failure, which kills the stereo system entirely. The dealer wanted $2,000 to do the repair but offered to sell me the amp alone for about $800 (with exchange of my existing bad amp). After doing my research on part numbers, I bought an upgraded used amp (p/n ends with 01) from eBay for about $325. Described as remanufactured, I was hopeful it had already been through the dealer process but the amp that arrived was missing the remanufactured sticker. Bummer. But I decided to go ahead and install it. It took me a little over an hour to do the work. It now seems to work fine. Here's a link to the full photo set.
You can also find more information on how to diagnose and replace your ML amp here and here.