Spool valves and gear pumps are not generally rebuildable. When they die you replace them.
Your loader valve is two handle operation. You can replacce it with the same thing for $189:
This Monoblock Hydraulic Directional Control Valve uses 1 Float & 1 "A" Spool. It has a capacity of 11 GPM. Free Shipping
summit-hydraulics.com
Or for $60 more you can upgrade it to a joystick. I think thats a no brainer:
FREE SHIPPING This Monoblock Hydraulic Directional Control Valve uses a Joystick, 2 Spools and has a capacity of 11 GPM. These valves are used to start and stop fluid flow into hydraulic cylinders or hydraulic motors.
summit-hydraulics.com
I have put something close to a hundred of these pumps on various tractors and they are the first place I look. This one will give you 7 GPM @ 2000 RPM and should bolt right up. You can go bigger or smaller for the same price. You will also probably need to replace the pump half of the chain coupler with one that matches the 5/8" shaft on these pumps - another $15.
0.85 cu in Dynamic GPF2014PA Hydraulic Pump, Gear Pumps, 0.85 cu in DYNAMIC GPF2014PA HYD PUMP, 0.85 cu in DYNAMIC GPF2014PA HYD PUMP Brand new,Dynamic,GP-F20-14-PA ,
www.surpluscenter.com
One last thought. I dont think that loader had a hydraulic filter and if not I would definitly add one.
Dan