Thanks for the response. I called a dealer for the service record. They report all scheduled maintenance done at the proper time by a Lexus dealer. About the only non-routine repair was a power steering pump this April, which they said was not surprising with it's age and low mileage.
We usually put about 10,000 miles per year on a car, so the warranty should last the three years.
The service contract covers a standard list of parts and systems, anywhere you have them fixed. It also covers towing "to the selling dealer or the nearest service location." The used car dealer claims that it will pay for towing to the Lexus dealer, which is about 150 miles away.
Also, the repairman at the used car place indicated that they are seeing more and more cars arriving with no freon (or 'non-freon') in them. Somewhere along the line a dealer is taking out the refrigerant. So that may be the only problem with the AC. We'll see.