The most wear on a blower occurs in the impeller housing which is usually irreplaceable, so I would want to check that out carefully. (How thick is the metal? How much wear so far?)
Where are the shear pins and how easy will they be to replace? I did a lot of cussing with my first blower if the impeller shaft shear pin broke. My Kubota takes 5 to 10 minutes to change.
I have a front blower, heated cab, hydraulic control for the chute rotator and an electric control for the chute angle control. I don't have to leave the tractor once I start blowing, until I clean it off when I am done. For me snow blowing is a lot of fun. The nastier the weather, the more fun it is. If I had a rear blower, manual chute rotator and angle controls and an open station tractor, it would be one of those jobs I have to do, but I would hate it. If I didn't have to snow blow very often, I could tolerate the pain.
To me the manual chute rotator looks too short, and unless you are blowing your snow into oblivion, you will need to adjust the direction. I would put the blower on your tractor and see how easy it is to use the chute rotator. I think I would want a longer shaft.
The price seems fair, but given it is barely the end of the snow season, I would take 6 crisp $100 bills and see if the guys takes them from your hand.
Below is a movie of my blower in action: