Congratulations on your purchase. I haven't sailed a Columbia 26 or any Columbia but I think you may have found a fine pocket cruiser. If you haven't already seen this, here is the sailboat data.com page on the boat:
It is thought that the COLUMBIA 26 is an extended version version of the COLUMBIA 24 and built largely from the same tooling.
sailboatdata.com
The boat looks like a Carl Alberg design but evidently isn't. The link to history of Columbia states that the Columbia 29 is an S&S design but is silent on the 26. The line diagram shows an inboard engine with the shaft exiting the full keel stub, prop aperture and a hung rudder. Lead keel - +1.
In the rigging stats there is an ESTIMATED forestay length which would be useful in planning a furler. Of course you need to actually measure it before ordering.
If you click the Columbia type next to the builders under sailboat links you'll get a history of Columbia which I enjoyed reading. It is also a metaphor for the sailboat industry of that era (And some would say today, too). Boom and bust.
As for a manual it wouldn't have been much. A few mimeographed sheets with maybe a line drawing. Maybe some recommendations on running rigging. What ever they suggested in '63 would be obsolete today. I would not be surprised to see wire spliced to rope halyards.
The engine could be 63 years old. Hopefully. you can find some sort of manual for it. If you can find replacement parts for critical components it might be good idea to purchase them now. I think the C&C 25 Mark V has a Yanmar one banger so that could be a lead.