Exhaust manifolds removal?

["Stian Birkeland" <delorean@xxxx>]

I have discovered that the exhaust manifolds, LH and RH side, are very rusty. Now, that happens to every automobile that I know of. 

But - what worries me is when the time comes and I have to change the gaskets. It looks like the original fasteners of the manifolds (studs?) have rusted to an extent that they will be impossible to remove without screwing upthe aluminum block! 

So, what is the fix for this? 

How do you get out the rusted studs/bolts. I can already see that this is going to be a problem, so a fix would be very much appreciated. Then I'll doit right away before it gets any worse! If I have to drill out the old bolts/studs, then that will certainly ruin the threads in the aluminum block, making it impossible to fasten anything...or?

Many thanks,
Stian Birkeland
Norway

VIN # 06759