According to Texaco's website, "Super Universal Tractor Oil Extra 10W-30" is rated for use in transmissions, hydraulics, axles, and as motor oil.
Personally, I like to use specific fluids for their purpose. It seems to me that dedicated tools always do their job best. I like gear oil in axles, the universal tractor oil in the reservoir/gearbox, and motor oil in the engine. I have no empirical data this combination is superior, but it seems logical to me. To do a replacement of fluids you'll almost certainly use a 20 liter pail, and probably more. I'm all for simplicity through commonality, since I'm lazy, but I wouldn't want to try adding oil into my engine from a big 5 gallon bucket, spout and funnel or not. Using quart/liter containers of oil simplifies measuring the volume of fresh oil, too.
It seems easier to me to use regular motor oil for the engine, and then run the common fluid in all the other reservoirs if you like. A long-necked flexible funnel has been a boon to me. There never seems to be a way to fit the spout of a bucket anywhere near the fill reservoir on any of the Japanese tractors I own.
Congratulations on your new acquisition. I really like the "in-between" size of the 1610, and the Powershift transmission is wonderful compared to a conventional gear driven machine.