HELP! Exhaust Manifold Replacement Needed

[fordfarm]

I have a 1999 Expy w/5.4 and the passenger side exhaust manifold is leaking. The manifold studs are rusted nubs and can hardly make out the nuts from the rust. Has anyone here replaced a manifold like this? If the studs break off, will there be enough behind the manifold to get the remaining part of the stud out? Anybody have any advise, tips, how-to help?
Thanks