The JD X50 line of tractors are a very nice line. They were made for JD by Yanmar.
They are reliable and the Yanmar engine is nearly bullet proof. My 950 has 1700 hours on it and I haven't had a minute's trouble out of the engine. Just keep it maintained!
The four wheel drive is a great option, the mower is a good option, especially if it is a belly or mid mount mower. Just for comparison, I bought a 60" King Kutter rear finish mower for mine six or seven years ago and I paid around $800 for it used.
The blower is worth it's weight in gold. A 60" blower will run no less than half of the asking price by itself.
The only thing "special" that I can think of is to make sure that you run JD brand Hy-Gard Low Viscosity hydraulic fluid in these tractors. It is expensive, around $70 for five gallons, but it is what is called for by JD and it makes a world of difference in hydraulic speed in cold weather.
All in all, without seeing the machine for myself, if it is in as good of shape as you say it is, the engine has been maintained properly, and the tractor generally taken care of, I would say that it is a good deal. They are a lot of fun and great little tractors.
Let us know if you get it or if you can get some photos and more feedback, post away. Good luck!