What is the time and labor to replace the front seals? on 1999 Honda Accord

Mechanic says I need front seals. My question is how could he tell. I had him give the car a once over, and this is what he came up with. He also said I need a new valve cover gasket. How can he tell the leaking oil on the engine surface, is from the front seal and not the valve cover?

1 answer
The valve cover is higher up on the engine than the seals and a mechanic can follow the trail of oil and determine where the leak originates from.