It's not so difficult if you know anything more about hydraulic,cylinder construction and principle of operation...ofcourse it will be good to have someone who did it before and can show you what is going about...sometimes piston of cylinder is damage too and should be chaned because new seals in this case will be not enought.In my company workers often repairs lift,tilt and steering cylinders...sometimes we bild own cylinders.For the first time probably it will be difficult but it is the best or only way to lern how to do it.