Pull at least the left head and replace all the exhaust valves.
If the engine has more than 150k then I would advise doing both heads and renewing the valve guides. The labor to do one head is 18 hours, the labor to do both 26.
This is a real expensive job but if you are doing it there is only a small difference to updating a number of issues that eventually pop up: head gasket leaks from the left head and oil consumption through worn, hard to seal, valve guides are a couple that come to mind.
We do that job for around 2500-3000 depending on how many other things need updating like rocker arms for example. it would also include a new chain and rails in the top. I wouldn't worry about the bottom right rail unless the car had 250k or more (to change it requires removing the timing cover another 10+ hours labor.
Bosch Master, ASE Master, L1
33 years MB technician