If you push in the clutch pedal when the PTO is running, and it stops, it is not live.
Original trans oil was just 80W mineral oil with no EP additives and some of that stuff was brown. Near the same thing as non-detergent 30W motor oil. One some machines, adding a more modern oil can cause problems. Especially with a synchronized transmission or with wet clutches or brakes. As I recall, you have none of those issues in your 1010. Subsequently I supposed any 80W or 90W gear oil will be fine. I would not use Hyguard because it may be too low in viscosity and might result in some leaks. Hyguard it 10W or 20W oil. Whereas 80W gear oil is 30W oil.