Exhaust Manifold EGR
 

I recently decide to replace my EGR valve on a 1989 420SEL. In doing so, I removed the front pipe leading from the exhaust manifold to the EGR valve. When I went to put the nut back, which holds the pipe to the manifold, it seems the threads have become cross threaded.

1. How do I get the fitting out of the manifold casting, that the nut attaches to? It's quite rusty. Do I use a propane torch to heat the fitting? or do I try to heat the manifold? I doubt my propane torch produces enough heat to make the manifold casting hot enough to get the fitting loose. Any ideas?

2. Is it too risky to drive the car temporarily with the cross threaded nut on? Could the nut be blowen off by the exhaust pressure? What would happen if the nut was blown off?

Thanks,
Joe