Fark that seems cheap for a Lexus, I'm cutting myself right now.. Wholesaled mine off *again* to a mate for $9500 only just painted too. I know I could have got $14k. oh well.
Valve steam seals normally show wear around mid to high 250k. In terms of how to tell, does it blow any smoke on start up? or if they are bad under throttle, but not when you lift off.
It'won't really affect its performance.