Well I got the Kohler going this afternoon. Good sign. Had to replace some fuel lines that were leaking fuel out/air in and needed a good big, freshly changed battery to overcome the initial reluctance of not starting for several (?) years.
Now that I know its a goer, I have given it a basic oil & oil filter change - will only run it for a short time before replacing the oil & filter again. Original oil very very black & smelly.
Have removed the engine again, to facilitate replacing some of the transmission hydraulic hoses that appear to have been leaking.
Will test transmission, when I put the engine back in - if it works will replace transmission oil & filter. Fingers crossed.