If there is evidence of replacement on an e320, should that be essentially permant fix? (excluding expecting either to last 500,000 miles of course...)

Also, how much money should I "discount" a car that has not had this done or evidence of it being done?

How much do I need to budget for each at an independent (not dealer) if not done? I know there will be a range on the price...

Thank you!
-Andrew