Had the same problem just the other day but it wasn't just a leak as the whole oring for the bucket dump blew out and I lost over a gallon of hydro oil like right now. BTW A Five hundred pound rock hits the driveway pretty hard when dropped from about three feet.
Lots a luck with trying to remove the fittings without taking half of the tractor apart as the battery case is just about an inch above the fittings and is part of a large aluminum casting to which most of the tractor is bolted . You can replace the bottom oring but not the top. There is however a solution and that solution is called an angle grinder with a cut off wheel, takes about five minutes to cut the hole in the base of the battery compartment as opposed to five hours taking things apart. After the hole is cut it's a piece of cake getting at the fittings with a ratchet and a one inch socket. Strange how some things on a Kubota are metric and some are Imperial.
The lower orings cost .80 cents and the upper ones are $1.35 and the screw in fittings are $5.47 each, not sure what the lines cost as I replaced all of the orings and the screw in fittings but not the lines, hope this fixes it, if not the lines will have to be replaced as well.
This seems to be an ongoing problem with kubota hydraulics, in some cases replacement of the rings has fixed it, in some both the rings and fittings, in others the lines have to be replaced as well and in still others the entire valve body has had to be replaced. Anyway you look at it it sucks because if you can't rely on your hydraulics there is no point having them because it can get real dangerous real quick.