I too would post it everywhere. And not say they did a "bad" job. Keep to the facts ie , they said they would send you an estimate, never received. The said..... on and on. And identify exactly what happend and exactly how much was billed. Use the other forums too. You may have other cruisers that have had a similar experience. If you find one that had the same work done and only a 4 hour bill then you can look take that to them. I can't imagine how it would be 9 hours. At the worst I could imagine almost 4 man hours considereing that they may round up. Even 4 hours is tough. One hour at most to remove the shaft, 15 minutes at most to slide the new end on, and an hour to reinstall! Make take two to remove and two men to install but I"m expecting 30 min each. Of course they may be counting on coming to the boat to look it over, then going back to get tools, then arriving with the wrong tools and back and forth. I don't know either if you have to remove the rudder to remove the shaft but I'm guessing you could slide the fitting on once the shaft is out of the coupling and then put the coupling back on.

Just my two cents
Good Luck

Ciao