have just done one on my dads as we knackered it doing the seals on the Drive shaft you need to Cut the old one out or get a strong, large set of Pullers using the puller to pop it out or Cut it out like we did then get it in as far a s possible by hand then put the puller on to force it in to the hole, was a pig took us 2 hours to take it out with angle grinder, hack saw and air chisel and about the same to push it in
also i would suggest that if you have access to Gas bottles then Heat the Axle up and chuck the Ball joint in the freezer for an hour or so then drop it in and then press it in
hope this helps