I would not know what you would call hard. If you don't have the jacks and wrenches it would be very hard. If you have a good jack to lift the front and stuff to block the rear tires from moving, along with the wrenches it would not be all that hard. You will need to remove the radiator, front axle to start with. You will have to then remove the radiator mount and the front pulley. If it has the new style seal it can be changed at that point. If it has the old cork seal then you will have to remove the water pump, governor cover and the timing gear/ front cover/plate. The grooves in the crank will have to be filled with JB Weld or something like that. The old cork seal will have to be driven/pounded out. then the new seal can be installed. the gasket area will have to be very clean on both the block and cover. The cover will have to be put back on with care as not to spoil the new seal. You will have to pay close attention to keeping the seal centered as you put the bolts back in or the new seal will leak anyway.
With that being said you will have to decide if it is easy or hard.