I wan't going to tackle the project myself but instead have a contractor do it. I received two different responses from contractors, neither of which actually looked up in the attic, but I did tell them which way the joists/trusses ran. (I think they are joists rather than trusses) Contractor 1 gave a quote around $600. Contractor 2 said he wouldn't advise it which leads me to think either he couldn't do it the right way or that it shouldn't ever be done.
It would be nice to keep the opening in the hallway, relocating the drop down stairs so they run with the joists would put it in one of the bedrooms-yuk!