I had the same problem last year at 66k. I had bought the vehicle in 2010 as a lease return with the extended 3 year warranty. Of course, it was about a year over the warranty, but well under the 100k mileage. After extended conversations with Lexus in Torrence, Ca. they agreed to pay for the labor which came to about $2,500 and I paid the parts of about $500. Of course they found other things wrong, mainly cv boot on one side which cost me another $450.
Since this repair is of a known defect in the silicon sealant of the timing chain cover at the time of manufacture, I would go to the mat with Torrance for them to pick up the labor, especially since you are under the 100k mileage part of the warranty. Then, you should be able to handle the parts, whatever that cost is. My $3,000 was at an agreed upon price between Torrance and the dealer, so there may have been some cost sharing there, as opposed to being straight "retail!"
Good lick!