Questions about KMs and buying a car

What you need to do is get the service history of the car, there should be a service book and the current owners should have service recepts, get the car inspected by a mechanic first hand, get a compression test done, an inspection may cost you about $100 or so but that is good insurance a mechanic will see and advise first hand on any problems, if the car has been looked after with normal servicing and repairs as required there should not be an issue with it, But you really should get it checked out first, if the owners are not keen for you to do this then walk away and find something else, as they are probably trying to hide a problem.