Remove both cylinders (bucket or lift arms) not just leaking one and take to local independent hydraulics shop for rebuilding.
Dave
Perfect advice.
I did this a couple years ago. One cylinder on my B2910 was leaking (same tractor as the B7800) , and before I got around to taking it off for repair, the second one started leaking too.
Seal kit from Kubota was something like $60+ each plus shipping. I got my cylinders repaired at a local hydraulic shop for $100 each out the door.
Took less than a week to get it done. For me it was the easy and quick answer, as I do not have the tools or workplace to do it myself, and I was not interested in spending the time learning something I would soon forget before needing it again probably.
Granted my loader arms have cylinders too...but I know what I will do if they start leaking...LOL...take the easy way out! Especially since the cost difference is not that much.