You might have to replace the manifold or you might not. You wont know untill you get it off and take a look at it. If the manifold is warped you should be able to tell pretty easily.
The nuts are probably going to be rusted onto the studs and if you have broken studs those might be interesting to get off. Mine were rusted so bad that you had to use a smaller socket and pound it on with a hammer in order to get a good bite on the nuts. For the studs were just used lots of penetrating oil and pair of vise grips.
Good luck, chances are you are gonna need it.