JB - I would cut the full choked barrel. My reasoning is that it is much easier to get a replacement full choke 12Ga in the classifieds than a modified choke 12Ga. I'm only talking about the classifieds, not from the factory, which won't fit them to your gun for the reasons mentioned by quick.
Regarding the transfer bar/striker assembly which is in operable, I would take quicks advice and repair it yourself. It's really not that hard. If you don't feel you can do the repairs yourself, take it to a gunsmith, and have him also cut the barrel for you while your there.