Well, this has been resolved. My buddy "proconnor", who also posted to this thread, got a machinist involved. After the easy out failed to extract the bolt, the machinist milled out the bolt as close to the threads as possible.
I guess he crumpled in some of the remaining bolt, and then used a tap to to remove the rest of the thread that was left. From what I understand, it's good as new - no damage to the original shaft threads.
The machinist, who builds custom hydraulic cylinders for equipment, says that he recommends pure silicon caulk for bolts. I'm going to remove my blade bolts, and make sure that I coat them so that I don't run into issues.
I found that the shaft would have cost $110 alone, not including the effort to rebuild the gearbox.
The machinist was a friend of proconnor's, so he got away with a cheap repair.
Jesse