I've replaced mine, TWICE!
Both were bronze, now it's monel. (H34) Unless you know the history of your bronze shaft, it may well be bent. You might ask the mechanic what test he used to determine the diagnosis. The first shaft I had, was ruined because the #@$%& dealer didn't install the key in the coupling. The jerk! It came loose and we lost drive while trying to go under a local low bridge that had only one spot to pass underneath. The tide was also on flood at four knots. We just made it or we would have lost the rig. I replaced the shaft myself. The dealer paid for everything including my labor. The jerk! Anyway, when the boat was in the slings, I put the engine in gear and let the shaft cut itself off with my hacksaw. The coupling was ruined too. When the replacement shaft was found to be bent during a haul-out on Keywest, I went with monel. The damage to the second shaft had been caused by drunk guests that let a halyard go overboard and then put the engine in gear. Don't ask! I've told that story here once and that's enough.That shaft was removed with the rudder installed. The prop has to be removed first. Then the coupling has to be pressed off the shaft before it passes through the shaft log. I built a home made press out of bolts and socket wrenches. It's a pain. At the time, I thought the shaft was savable. Should have just cut it off. Also, for packing, I use that putty-like stuff called 'Lastdrop' I believe. Most marine stores carry it. Costs $35. It's been working for over 16 years on two different shafts with no service required. I haven't even needed to tighten the adjusting nut. And it hasn't leaked a drop of water. The shaft spins free. A perfect product.What else? Daryl suggested strut removal instead of dropping the rudder. That's my first choice too unless the rudder needs work.