Loader John Deere 1120 hydraulic oil type and how to check

[Gordk]

I have recently purchased a John Deere 1120. I have no operators or service manual. I believe all hydraulics e.g. steering, the loader and the rear lifts are all operated from the trany/diff oil. The dip stick is located on the right side below the seat. It has a red coloured oil that looks like car oil.
My questions are
1. I'am i right on what the hydraulics run?
2. What is the right type of oil. Is Universal tractor fluild (TDH) good oil for the hydraulics on this unit?
3. The unit has a "park" on the transmission - so do you check the hydraulic oil cold or with the engine running?

Thanks.

Gordk