I would NOT RUN that hydro! PERIOD! The regular Hytran oil is a 30 weight and it is the fluid for both the hydro and the differential. Regardless of that fact for 200 bucks I would pick it up either way. Even if the hydrostat is bad a good 50" deck is worth $200 in itself. You can get a used hydrostat pump quite reasonably and would still be ahead of the game for what the tractor is worth.
If you go for it before anything else drain the fluid out of it and put in fresh CaseIH Hytran and a new filter. Post up some pictures of it and we can give a better idea of its worth. I had a 1450 with a 44C deck at one time and could quick myself for getting rid of it.