Well, from an engineering standpoint, as I see it:
The replacement section is already on site;
The interior finish reeks of smoke and hazardous particulates, and so is likely already out...
Just disconnect the various lines, unbolt the damaged section, and bolt the replacement section back in, shim to align as required. Replace or renew the lines. Cover with new interior.
Whisk the damaged section back to the factory; make whatever repair might have been contemplated at some time, and test at leisure to see if it would have worked.
Why take any chances? So let people think that a marvelously cheap repair has been devised, since that seems to be the drift right now. But just do the sensible thing.
We used to sometimes say in the engineering office that sometimes it's cheaper just to do the job. And I'd say, it always was.
OE