Not often a head gasket will leak oil, but yes it certainly can happen. More often it is coolant they leak, which can during use accumulate dust and appear to look as an oil leak. But yes, it could be oil for sure.
Not a big job, wouldn't hurt to replace it, give you a chance to have a look inside as well. Then give it a top end set afterwards, and you should be good to go, they are good little tractor
It is definitely engine oil. I also thought it to be strange to leak engine oil from there. The tractor isn't used a lot, but I don't like oil leaks so it will have to be looked at when time permits. I really like the tractor except for the gearshifting.
Yes the syncro range shift patterns leave a bit to be desired, not sure what they were thinking, like who would ever want to shift from 5th to 2nd lol. Just have to remember, it's best to completely stop when shifting stations. If it is grinding between the forward gears within a station, syncros are wore. The later ones were syncroed between reverse as well. If the shift linkage is loose and the quadrant and lever is wore in the dash, tightening things up will make it better
Most times it shifts fine, even between forward and reverse, but sometimes it wont go into any gear and you have to shut the tractor down and begin again. I learned that if it wont go into gear it helps to bring the engine down to idle. It sounds worse than it is really. I always wanted a 4020 so maybe this is the start of my collection.
The older Deere engines have a pressure oil passage at the right rear of the cylinder head/block...this supplies oil to the rocker-arms/top end of engine. Fairly common for the engines to leak oil along the right side anyhow as that's the side where the push-rods and stuff are.