One hydraulic coupling(scv) outlet is leaking(pretty good stream) even without moving the lever in the cab. I've never fixed these before, usually let the JD man do it. At 200.00 a service call I might give it a try myself. Is that all I need are those plastic packings and some orings, is it better to take them off the tractor and work on them on the bench? thanks for any insights! TIA/ bob