It really depends on the place. Shop around and see what u find. Start with shops that are known for mustang work. Let us know what kind of quotes you get.
Or just install it yourself. It's not all that hard...
A Cobra/Stang specific speed shop that isn't paying for magazines,websites,advertsing etc.. should charge in the $300 range to pull you factory motor and put it on a stand...
Are you wanting the shop to transfer all pullies,accessories,blower,etc.. to the Re-man?