A little bit of work but no where near the $6 g estimate;
1) remove your shaft - should have a flange connection on the inside before the transmission
2) Get a piece of pipe close to the diameter of the stern tube shell and punch the tube out. It will most likely be easier to do this from outside since you can get a better swing at the pipe/drift. If this prove difficult, use a reciprocal saw to cut a stem to stern slice out of the stern tube and then use a chisel to collapse the tube and pull it out.
3) Take the external cutlass bearing housing along with a new cutlass bearing and a new
stern tube to a machine shop.
4) Have the machine shop clean up the threads on the cutlass bearing housing and if necessary rebuild
or cut off the damaged thread area - whatever is required to get a good solid fit between the new stern tube and the external housing.
5) When you fit the new stern tube into your shaft tunnel, keep in mind any deviation in length that was made by the machining, ie if it was necessary to remove 1/4 inch from the threaded portion of the external housing, then the stern tube will have to be fitted so that its final mounted position is 1/4 inch further astern then the original was. Thixo or other epoxy
repair/bonding can be used to fill the minor space as well as secure the new stern tube in place.
6) Dry fit everything together. If it looks good, install the shaft, slide the new stern tube over shaft, coat the stern tube and mating surface on the stern tunnel with suitable epoxy
cement, lightly grease the shaft and slide the stern tube in place. While the cement is still workable, mount the external cutlass bearing housing and screw the external threads into the stern tube. Snug up then back off 1/4 turn and secure the housing with the upper and lower bolts.
7) Allow ample time for the cement to cure. Then move the external housing back on the shaft and grease the shaft. Clean up any excess cement. Reassemble the external bearing housing to the stern tube snugging the screw together coupling with a drop of anaerobic thread sealant
. Do not overtighten, snug is good.
8) Pat yourself on the back for doing the job right and saving at least $5 G