Craig Briggs SN 68 Sangaris
Here are some pictures of the C-Drive with the GRP fairing removed around the gear box cover to allow unscrewing the bolts and removing the cover which then lets you slide out the entire prop shaft.
Of note is that the oil is totally contained in the metal housing. The GRP outside is solely for structural support, positioning and shape. An oil leak then, is definitely going to be from a seal, be it the rotary shaft seals, the wearing-out-bearing's inner O-ring, the drain plug seals or - unlikely, if it's never been removed - the gear box cover I've removed in the pictures. I suppose an oil leak from one of the seals could drip into a crack in the fairing, if there was one, and look like it's the fairing leaking.
Also of note is the puddle of "milky" oil right next to the shaft and bearings which are in pristine condition. The oil had been milky for about 9 months before I did this work and it clearly did not cause any rust to form. That's likely because the mixture becomes totally emulsified by the gears. Out of curiosity I let it stand for days and there was no water separation, just like the oil in homogenized real milk. I think that suggests there's some breathing room on the timing of oil changes even if your's becomes milky.
Hope this is helpful.
Craig SN68 Sangaris