Just a couple of my own comments followig Tim's sound advice. There is no need to do aything with the spring. Just remove the driveshaft after undoing the 3 hub nuts with the special tool. Remove the circlip fixing the inner castellated nut and carefully drift out the bearing.
However, the bearing inner nut can be a real problem to undo it even with the special tool and a lot of brute force. If resistant to all efforts, it is necessary to remove the suspension swivel (after disconnecting upper and lower balljoints, again a special Lancia tool helps here but not essential) and try to undo the nut on the bench. In my last case (after using 700 Nm torque...), it was necessary to go with the swivel to a lorry garage to use a giant power wrench. In this case a hydraulic press is great to fit the new bearing.
Removal of the top balljoint from the S1 wishbone is very difficult in situ. Best to drop the subframe and remove the wishbone, not a 5 min job. Good luck, Andrea