i see it has the original pto 1/18 shaft, not a replacement... also see a home made drawbar bracket, as well as a welded manifold.. non of wich are a immediate cause for concern as long as they work.
the pto shaft seal is a 15 minute fix.
if it is overfull, i'd worry more about oil on the brakes vs the pto.. I see the oem oil dipstick for the common sump rear end is gone and something else stuck in there.
with machine off, grab pto shaft and see if it has in / out play or side to side play.
if it has in / out play then it has a possible bad bearing, bad wear ring, slipped or broken circlip, or damaged bearing carrier.. if side to side play, then bad bearing. bad bearings will allow seals to hog out.. pto shafts with in / out play will eventually do 2 things, 1, mushroom the end of the shaft internally and make it hard to remove, 2, walk it out of engagement and eventually damage the pto shaft internal spline, and the sliding dog clutch.
if none of those are an issue and it is just a leaky seal, again.. 15 minute fix, and about 17$ for a new seal and gasket.. drain rear end oil ( 5 gallons - refill with 90wt gl1 / 3 oil, or 80w90 oil meeting the gl4 / 5 / mti spec that states it is yellow metal safe, or any UTF fluid meeting the M2C134 spec. ).. 4 bolts and you snatcht he assy out, rmove rear circlip, tap pto external stub end down on a pice of wood on the ground, bearing carrier and seal fall off the pto shaft and bearing assy, drive old seal out, drive new seal in, ( 2 -5/8 socket makes a great seal driver ), reseat by greasing seal lip and setting pto lone end down on a piece of wood onthe ground, short end with bearing facing up, set bearing carrier and new seal on top, then tap down witht he shaft ontothe wood and the shaft will seat into the seal and carrier.. reinstal circlip, clean flanges up for gasket, slip back in with new gasket, bolt down, add oil.. etc.
soundguy