The correct fluid to use in the transmission, hydraulic reservoir, and rear differential section is Universal Transmission Fluid (UTF) equivalent to Ford/New Holland specification 134D. This is Ford/New Holland approved practice. You can get this fluid from Tractor Supply Stores, auto parts stores, Wal-Mart, etc. In 5 gallon buckets.
For maintenance items, you need to get an owners/operators manual for your tractor. Tractor supply stores should have them, and ebay usually has a good selection. Not expensive ($20-$25).
Transmission fluid level check plug is a small square-headed pipe plug right side of the transmission. Transmission capacity - 5 qts. Filler cap is a large plug near the shift lever. Drain plug is under the transmission.
Hydraulic reservoir fluid level is checked with dip stick. Hydraulic reservoir capacity 8 qts. Filler cap is under the seat on the left side. Drain plug is under the hydraulic reservoir.
Rear differential fluid level check point is a small square-headed pipe plug on left side rear. Rear differential capacity 8.5 qts. Filler cap is on top of the rear center housing just behind the seat. Drain plug is under the rear differential section.
One often overlooked small reservoir is the steering gearbox. It takes 80-90 wgt gear oil. Less than one quart. If it is leaking, try cornhead grease, available from John Deere. Somewhere on the steering gearbox, there is a small square-headed pipe plug to check this fluid level. Fill box through this port till full to this level.