I have dabbled with hydraulics a bit and my thoughts are if you have the spool block ( leavers ) for the crane, there should be a pressure relief valve on that, you will need a oil tank and filter as well, with the pump make sure it pumps in the right direction in relation to its rotation, as some pumps will NOT pump in both directions depending on the rotation, to do with pressure feeding the bearing surfaces in the pump. So the only other thing is the volume of the pump, the one you have might be too much for the crane ie too much volume means when you operate the leavers it pumps too much too quickly so the crane arms and slewing will be unmanageably too quick. Or its too small and the crane will take for ever to move.