... wonder whether I'm being realistic & responible
enough intending to be able to handle a 25 ft motor vessel single
handed as far as mooring, etc is concerned.

Not at all. Practice may not make perfect, but it'll make better.

I'm more concerned with backing up my trailer & boat (26'OA) into my
driveway than I am about docking boat.
Maybe the "practice" rule would even work better if I just wrangled the
trailer without the boat on it several times til I "get it right"