The 3600 was a slight upgrade of the 3000. The internal hydraulic pump was about average for it's time, but would be considered a bit smallish by todays standards. That probably accounts for the slow up cycle time on the loader. Those pumps made adaquate pressure, just at a lower flow rate than is common on todays tractors.
I owned a 3000 from new in 1973 (72 model tractor) until 3-1/2 years ago. During all that time, I had a Kelly loader on the tractor. When I finally sold it, the reasoning was a VERY worn out front end. (axle center pivot, spindles, steering, even the axles sagging) Loaders can be tough on that front end. (same components on 3000 & 3600) Make certain front end is still in decent shape. (If you can, jack the front end up, taking all weight off front axle and check for slack in any wear points)
That is EXTREMELY low hours on a tractor of that age, but not unheard of. (I've been watching an auction coming up in Illinois with a 1982 Deere 4440 with FIFTEY SEVEN hours on it!) Look at those wear points on clutch/brake pedals, running boards, ect, as well as examining the STEERING WHEEL for wear. Look closely at ball ends on 3-point hitch, and the hitch pin hole in the drawbar. Excessive wear there would probably indicate more hours. It's a piece of cake to get a new dash panel for that tractor. That'll give you a new proofmeter/tach, one with a fresh start and a bunch of zero's.
Price is a little steep, but if the hours are accurate, and the loader is in decent shape, not too far out of line. Really good tractors of that era command a nice price.