Cusser
+1y
Loosen/remove the fill plug on the side BEFORE you drain the transmission oil (iIf that fill plug is stripped or can't be removed, you'll know why).
Fill with 80W-90 gear oil, buy a pump that fits on the container. I use Valvoline gear oil, sme for the differential.
I've had the clutch pedal not return, don't worry about that now, install the engine first. Typically that's indicative of clutch cylinders, but try bleeding the clutch system first.