Hi Graham
I've done the job on my Alpha One drive but not the Cobra and I agree with Shibbs, crack on.
From the looks of it watching the YouTube videos it seem fairly straightforward, but I have a word of advice first. If you are planning to do work on your engine and drive, if you haven't done so already, invest in some proper marine grease and some sealing compound, not a sealant but a non washout type of greasy substance used for sealing out water but never goes off, great on nuts and bolts and for area's that require a good hold but you may want to undo in a few years after submersion in the briny stuff. My choice over the years has been Quicksilver 2-4-C marine grease with Teflon, it is completely waterproof and does not wash out at all, plus Quicksilver Perfect Seal, its very expensive but you will never use a can and it lasts forever and can be used for a number of different applications too. It's extremely sticky and will make a right mess if you aren't careful but then that's what you want in a marine environment.
This is a good tutorial how too, only thing is they don't give the measurement for the adjustment at the engine end, they suggest you have a gauge tool, but most cables are adjusted by a ruler usually 6" from the middle of the brass barrel anchor.
https://www.nlamarine.com/pages/omc-cobra-shift-cable-removal-installation-adjustment-instructions-guide Hope this helps

PS, This may be teaching your grandmother to suck eggs but remember, the two bellows that can sink your boat are the UJ bellows and the Lower Shift Bellows. So be extra vigilant when sealing off the shift bellows and also careful if you have to remove the UJ bellows, in fact unless you know when these were replaced I would replace them both.