That's a good question. Not sure where to go to get the power. Might be best to go straight to the battery. The winch will come with two heavy battery type cables with eyelet ends that can be bolted to the tractor battery cable ends where they fasten to the battery. The ground wire could be fastened to the frame of the tractor if it is easier to do. But the power cable needs to go as directly to the battery as possible. I don't like to use the starter solenoid connection because you risk causing corrosion at that location and possible starting problems. Then the winch will have a hand held, usually 12ft long control cable that plugs into the winch.
As for the dump trailer, again, you need to get power as close to the battery as possible and run very heavy wire to the rear of the tractor. You might want to research the trailer system to find the amp draw needed. That would guide you to the wire size and fuse size needed. I would avoid trying to get power from the tractor wiring system at the rear. I don't think there is anything back there wired or fused heavy enough to power your lift motor. My M9540 has an electrical plug at the rear for trailer use but I'm sure the circuitry isn't heavy enough to power a hydraulic lift motor.