I may be out of line here but I had a 4010 and 4020 and replaced the seal on both. Recalling from years ago, there was a snap ring holding the PTO shaft in place which you remove, catch about a pint of oil, reach in with a curved pick and pull out the old and replace it. I didn't have to drain the 15 gallons of trans hyd fluid.
I do remember the 20 had the dual PTO speed option. Don't think the 10 did. That may make a difference in having to drain or not. Obviously the dual PTO was designed for field speed change so they sealed the PTO from the main sump.
I don't know about the 3000 series.
However, I'd bet TX. Jim does. Give him a yell.