I disassembled the unit, but it was arranged differently from the Escalade one. I had to drill out a few nubs (from factory punchings) on the inside that prevented enough movement of the CD and DVD readers. It also required slightly forcing out the front part of the frame in order to lift those components out and reach the cable connections. Once able to do that, I was able to follow the procedure in the Escalade link to access the eye and clean it with alcohol and lens tissue.
Reassembled it, then reinstalled it today. Tipped the screen open using the 'eject disc' button on the screen. Inserted my new nav disc (from eBay), but had to push it in all the way because the device didn't grab it as it was supposed to. After it went through its resetting sounds, the screen displayed the message that the update would take "less than 10 minutes" and not to change the position of the ignition key or eject the disc.
It eventually also shows a four-section progress bar, with the first section colored in. But it never gets beyond that. It proceeds from there to briefly display something in JAPANESE, then goes blank and starts over. I can't get any button, MENU, NAV, FAV or power to leave the loop. I can't turn it off, even after removing the key.
Had to locate and access the fuse panel and remove the 15a Radio fuse. (The 10a Infotainment fuse did nothing.) Wasn't that a joy, considering where they put that fuse block!
Am I stuck now with having to pull the unit and send it for repair?