You will probably end up having to remove the brackets for the A/C, they make it hard.
I wouldn't recommend putting gasket sealer on the head side of the motor. Most problems with leaking valve covers are over tightening. They only need to be a little tight, especially with a cork gasket, I don't have the torque specs, but I am thinking something like 15 INCH/lbs
I would put a little sealer on the valve cover (if that is what you were talking about) to easily put it back on without holding it.