Sure wish my tractor had been stored indoors! The Yanmar green might polish out to look half decent but that Great Bend loader is hopeless.
The concensus here is run tires at least till you see cord. There isn't a safety hazard like a highway vehicle. You probably have several years left.
Power Service additive helps cold starting. You may not need it. AutoZone stocks it where I live.
Year model: The first-series tractors had headlights bolted alongside the radiator. Those tractors were green. First-series ended about 1978. Second-series had headlights side by side in the top of the grille. On the Japanese-market tractors, they started painting them red at that point. The tractors for the US market (YM195,YM240) continued with green paint through the end of second series, last sold about 1982 (?). This may be a year or two later than the 2 cylinder models were superceded in Japan.
Yanmar never defined year models but the parts books show four revision levels after 1975 so you can estimate the year. On the US ones, the final revision is obvious with an external pre-cleaner ahead of the air cleaner. Mine is level 3 with the air cleaner on the intake manifold, sold in about 1980. When you see a parts book you can match some features on your tractor to the revision levels it shows. Always provide engine and chassis number when ordering parts.
Enjoy your new tractor!