Replace Wheel Bearing Instructions

I have a 2004 Kia Spectra that is making a grinding noise from the front wheels. My mechanic told me today that it needed a new right front wheel bearing and it would cost $265 installed. Is that reasonable? I am supposed to have a 10 year, 100,000 mile power train warranty with Kia but don't know if it would cover the wheel bearing. He also said I have an oil leak at the valve cover that would cost $125. Again, reasonable? I have been smelling what I thought was gas in the front compartment when first starting the car up but he says it is probably the oil on the engine.