oil leak on 2001 Toyota Corolla

I have oil leak under the hood. They are saying it is possibly engine value covers. What happens if I don't stop this leak and how expensive is it to repair?

2 answers
If you don't address this leak you will have to watch the oil level, So it doesn't get too low and you can check the repair estimate here www.repairpal.com/estimator put in you vehicle's info and choose valve cover replace
It takes .8 hour to replace the V/Cover gasket and plug tube seals ($35 parts) if its not been done recently the valve clearance should be checked while the Valve Cover is off.