Don''t pay somebody $200 to replace one header gasket. Thats crazy. You don't need to remove the intake or valve covers. . The first thing I would do is find out where the leak is before you start swapping out parts. Is it the headers at the head or collectors?
To remove the header, just remove the air box, intake tube, Spark plug wires from the plugs on that side. You will need a combination of 7/16 wrenches and thin wall sockets for the header bolts. The rear one is a PITA to get to. If you still have the smog crap on, it is much easier to remove them for access. put masking tape on the vacuum lines and label them for the TAB and TAD valves so you know which one goes to which valve.
If your flanges are straight, there is no need for any fancy gaskets or RTV. To be honest, the stock ford OEM copper gaskets are some of the best and can be reused over and over if you are careful. I recommend either Percy's, Felpro 1415 steel reinforced, or Mr Gasket ultra seals. The key to no leaks is to make sure the flanges and heads are squeaky clean.
I soak the Felpro gaskets for an hour in water before installing them. That makes them expand and not crush as much, They also seal better when the engine heats up. I also use on stock or iron heads a 1" long SS allen head bolt and lock washers. Tighten them up from the inside out. Just snug them down and then tighten them down a bit. You don't want to snap the bolt. Go back after a few heat cycles and then after a few weeks. Do this and you will never have a leak.
