I'm wondering what I can expect repairing a valve cover gasket will cost?

 

If you do it yourself, probably not much. If you have to go to a shop and have it done, figure at least 1.5 hours minimum. You don't give us a lot to work with, so it's a general answer. The v8's cost more than the v6 usually, air conditioning can add more.

 

recently got a quote for I think 300 for a 99 f250 with the 5.4, they said a few things have to get taken out on the driver side to do the job. So if its anything like that I wouldn't be surprised if it ran that much.