1, sound slike you really.. really need to get a service manual now that you have ID'd your machine to be a 00 series.
I&T fo-20 manual covers 55-64 machines.
leaking hydro oil.
lets start here:
yes.. the machine has a hydro sump, for it's onboard engine mounted pump.
pump is onthe back right side of the engine.. there is a small plumbing manifold that connects the pump tot he front of the trans casting.. from there internal tubes run thru the tras casting back tot he next casting.. the center section.. that houses the hyds compartment ump front ( under the seat ).. rear of that is the diffy.
common leak points for hyd oil would be from the pump itself.. or the 2 plumbing connections.. 1 at the pump.. 1 at the trans.. there are orings there.. etc.
there is of course a hyds drain plug unde rthe center section that COULD leak.. as well as a cover where the relief lives.. guess that could leak... there is a fitting I believe near the base of the casting.. a pip plug.. guess that COULD leak.. from there go up and you hav ethe hyd cover.. pressure flows up to the right side of the cover.. there is a gasket and couple orings there.. that COULD leak out the side of the casting... at the front of the hyd cover is a 3x5 blank cover with a handfull of orings under it.. that COULD leak as well.
now the less likely possibilities.
it could be leaking hyd fluid out the dipstick because the sump is overfull.. possibilities are water in the sump.. or a perforated suction line inthe tranny, lett the hyds suck the tranny low and deposit the oil into the hyds.
also.. many people use the same oil in the tranny, hyds and diffy.. so the hyd oil you see COULD be tranny oil, coming from a leaky trans input shaft seal, and leaking out the weep hole in the base of the bellhousing. ( engine oil can leak out a rear main seal and come out the same hole.. etc. )
lastly.. given that the same oil could be used.. there are a few other leak points at the rear.. diffy drain.. . un.. i guess axle seals if the diffy was way flooded.. and of course the pto shaft seal.
you will need to see the drip and follow the oil track to narrow it down.
PS.. the 00/01 are very good machines, given good maintenance.. ther eis no endemic eak point in the hyds.
given lack of maint.. the most common critical hyd failure is a perforation of the suction or pressure tunbe that runs in the trans, allowing the sump to be pumped full or run dry.. this is due to water int he system rusting pin holes thru the thin tubing. various fixes available.. some less then fun.. some dicey on how goot they work.
post back more info or questions and we can help you.
probably no failure or fixes on a 55-64 that have not been done umpteen dozen times , collectively, by the membership here.