Exhaust Manifold on my 2000 Mustang V6

[tobence]

I have a 2000 Mustang V6 convertible that I know for a fact has a leak in the exhaust manifold on the passenger side. A couple questions.

First and foremost, the dealership told me it's gonna be about $450 to get it changed out. Is that a ridiculous price and if it is that much would it be cheaper to put headers on and whats the difference?

Second, could that be the reason that my car is now idleing a little weird? I know that if there is a noticeable leak then it can affect the mass air flow because it isn't syncronized perfectly with the flow of exhaust anymore.

Thanks for any help you can give, i appreciate it.

[AltecZX2]

you have to think that 450 would include getting a new header and seal right?