Silver Flight,
You only have to loosen the shaft at the coupling and slide the shaft back. The fact that the transmission was replaced may make the undoing of the shaft and coupling easier. I found that to be the most difficult and time consuming in both the boat I have now and the C30 I had before that.You will have to loosen and remove the wire and dog bolts clamping the coupling to shaft.
I had to use a short rod to push the shaft free from the coupling and used a longer coupling bolt to tighten the coupling back on while the rod assisted pushing the shaft out of the coupling. This had to be done several times and is a slow process. There is not enough room to get at the shaft to drive it out.
Once you are free of the coupling it is pretty easy. Replace the hose and the clamps and clean up the coupling and reassemble.
You mentioned you replaced the flax and you might want to consider using one of the new type which have teflon in them and are dripless. I did 4 years ago and the new style supposedly can last for many years without replacing. I found that there is no dripping and the shaft is very free turning.
On the other note of your muffler. I think the exit hose may last indefinately but the shorter one from the engine to the muffler you may want to replace with the "Hump" hose. I did this past spring and it is a softer hose that does not transfer the engine vibration to the muffler because it has more flex. I am quite pleased with that change. You can find these hoses at Catalina direct.

Welcome to the forum. If you could take a minute and fill in your UserCP (top left of the page) with an auto signature it would help members answer your questions. Things like where you are, salt vs fresh water, in water all year or part year, rig type (standard or tall), keel type (wing or fin), engine type, etc have a big impact on advice given.

In general though, if that rubber hose, or any rubber hose in the exhaust or engine cooling system hasn't been changed in 20 years I'd be changing it. That particular hose is all that is keeping your boat afloat. It should feel pretty hard, if it feels soft at all or has any visible sign of damage or bulges I'd change it ASAP.

Changing it is not a big deal. Shaft can stay in but coupler has to be taken off, if the coupler if old as well you should change it because they wear, it may have been changed when the engine/trans swap was done though.

You will need to lube up the piece of fibreglass the hose slides onto with soap, it will be a tight fit. Make sure it is straight once you get it on. You should check engine alignment if you change the coupler just to ensure it is OK.

If you repack in future might I suggest looking at the newer packings like Gore GFO? They perform much better and last a lot longer than old style flax though they do need more care taken in installation and break in than flax does.

[url]http://www.gore.com/en_xx/products/sealants/packing/gfo_packing_fiber.ht...
Link to Gore for the flax that is very good and highly recomended