Surveyor is right. The hardest part of the job is pulling the prop shaft (getting the prop shaft coupling off the shaft). You may be able to force the shaft out of the coupling by removing the bolts holding the prop shaft coupler to the output flange on the transmission output shaft, sliding the shaft away from the tranny, then putting a socket (or some similar-shaped object) against the end of the prop shaft, replacing the bolts, then tightening them, thereby forcing the prop shaft out of the coupling. You have to be careful not to bend either the prop shaft coupling or output coupling. As drastic as it sounds, it is sometimes easiest to cut the prop shaft.
After the prop shaft coupling is removed, the rest is easy. Pull the shaft, replace the shaft log rubber tube, replace stuffing box, replace prop shaft, attach coupling, align prop shaft. This is a good time to replace cutlass bearing if it needs it, and to repack stuffing box.
1977 C&C 30 Mk 1 hailing from Port Clinton, Ohio