Be aware of the other little things that wear out with age and miles.
drive it on a road with some dips and bumps (not smooth). Listen for creaks and how it handles. If its noisy or jumps a little, it may need bushings and or shock mount cushions.
Bear in mind that nothing on a Lexus is cheap to replace or repair.
Also, the insurance is going to likely be higher than a same age non lexus.
As an example, i had a 2 year old saturn and the lexus insurance is MORE. The lexus is a 93 sc400.
They are good cars but they still are getting older like every thing else, not just the motor.
Good luck ;)