We used to have a 9N when I was a kid. It was a nice tractor for it's size. Ours had some 3pt problems also. I finally rebuilt the lift. I was only about 17 at the time and the first time I had ever done something like this. WOW! that arm assembly was heavy.
Our had leather seals that we had to order from the local tractor place. One thing we did not like with our 9N was that the 3pt did not work unless the PTO was engaged.
Later on, we had trouble getting parts. We had real problems getting the throttle linkage. The last straw was when we needed a new carb ... finding one of those up-draft carbs was next to impossible. The tractor place said they were no longer available since our tractor dated to around 1939. Then, that tractor place moved and later changed brands.
We also had to replace the gas tank and the radiator. We could not get originals of these either so we made a gas tank out of a beer keg and the radiator came from an old Rambler.
I still have shoulder problems from cranking that thing with the hand crank because the started was also toast. We finally replaced it with one that was rebuilt when we converted the tractor to 12V. The starter was still 6V and would really spin that thing!
All-in-all, if you find a good one, they are fine tractors ... if you get one that needs a vast amount of work, be prepared to do ALOT of work.