Morris Minor Owners Club

Trying to do some work on my daughter car. Noticed some oil leaks from the rocker box gasket. Took the rocker box cover off and noticed an area of black carbon (?) deposits above cylinder 3 /4. My initial thoughts are that one or both exhaust valves are “ leaking”. Any thought’s please and any suggestion as to the solution. The car seems to be running reasonably well although I am having to replace the rear core plug ( rusted through), and while I am at it I am going to replace the water pump, thermostat and radiator tubes.
If, as I suspect the exhaust valves need replacing….all cylinders or just the two which seem to be leaking….my question is …. is this a job that I could tackle ( I’ve had the cylinder head off my Morris and put it all back OK…)..or is it a job best given to a suitable garage.
Any help advice please.

There is nothing wrong with the deposits inside your rocker cover. A most usual occurrence.
As the car is running reasonably well I would leave well alone until there is a real need to remove the head.
Replacing the valves is a task you can do yourself. You will need a valve spring compressor. There are plenty on 'e' bay and a torque wrench.

As always thanks for your prompt reply. One less thing to worry about.
Best wishes.