Hi, the labor allowance to replace the head gasket is 6.6 hours. I'd estimate 8.0 hours in the shop plus extra for an oil and filter change. A valve job would also be additional. We normally send the head to the machine shop if it needs a valve job. I'd estimate an additional $200 at the machine shop plus parts. If you are pulling the head I'd suggest replacing the timing belt and possibly the water pump and thermostat. You would need to add an additional 4.5 hours to do the belt as the front bumper needs to be removed. I'd add an additional 0.5 each for the pump and for the thermostat.
Please let me know if you have any questions.