Yet another purchase question..

[Yaris17]

So, after reading everyone's response to a potential buy on a wrecked yarîs I continued my search.
I came across a 2008 Toyota yaris hb blue with 86,000 miles all weather package cruise side air bags automatic transmission from a middle aged couple that purchased it new from a local Toyota dealership.
The man is a pilot and certified engineer. The miles on the car are mostly highly driving for his job. Always had synthetic oil since new. Has new tires and drives good.
Issue: the air conditioner "fell out" according to him while he was driving. They have extended 100k bumper to bumper warranty. Shop bill was 1,700 to replace ac. Was covered under warranty. Is this normal? Should an ac quit or fall out like that?
The couple seemed really nice and said they would take 8,500. Does this sound reasonable? Should I be concerned buying a car with 86,000 miles that's only 3 years old?
They also said that would pay and have the 90,000 mile service done at Toyota before I got the car if I was interested.