Wheezer,
You probably did pretty good. You can't buy a decent lawn tractor for that price. Worse-comes-to-worst, if it is an American Yanmar, you can part the thing out for far more than you paid.
Yanmars are really great tractors that are real easy to repair.
My only concern is -- is it a Yanmar 187D? A good friend of mine here in West Virginia -- and we aren't that far from Western PA, knew I had a high regard for Yanmar tractors. He recently came to visit and proudly told me that he bought a 187D with about 400 hours. He says the decals show it to be a 187D.
I still haven't seen the thing. He said it looks like new. But, he insists that it is two wheel drive! The seller told him the "D" stands for "Diesel." (For any newbies, the Yanmar "D" stands for 4WD).
These tractors are about 25 years old. 860 hours is certainly possible if it was a one-owner tractor, and used for occasional grading and snow plowing, and maybe a little mowing. Figure 40 to 60 hours per year for most non-commercial users. If it really is a 187D, with a loader, it is worth well more than double what you paid for it -- once the transmission is fixed.
If you can, post some pictures.
Good Luck,
Knute