Look on the loader valve. That's going to be the easiest place to work. It may look something like this one, which is very common design. You see there is a relief valve. The ports on that side are for pump pressure supply. On the opposite side are outlet (or return ports. You should have two lines connected on that side. Those are the two you want to switch. Those ports could be marked. One with N one with T. Leave the other five lines alone. In most cases you won't need to mess with the lines on the tractor.
2 Spool 10 GPM Joystick Loader Control Valve w/Float Chief 220957, Chief, 2 SPOOL JOYSTICK LOADER CONTROL VALVE WITH FLOAT Brand new, CHIEFChief,220957,