Cutting A Cat Out

Could  anybody tell me how difficult it would be to cut a severely
clogged cat that's also rattling out of of a 2" exhaust system using a
hand-held utility saw with a metal blade, assuming there's enough room
to operate?  

And if that's not to difficult, I'd also like to know how difficult it
would be to temporarily clamp a piece of pipe into the space where the
cat was unti I can have someone weld a new cat in.

Thanks very much in advance