You will have difficulty retaining the spring on an S1 without a proprietary tool (lets call it A) which extends the spring housing (S2 have this extension in effect with the upper bump stop). Even with this tool there is another tool to separate the ball joints after undoing the the upper ball joint securing nut. Commercially available is a pickle fork type that can split the joint from the arm. The ball joint then needs to be extracted from the arm If original it could be rusted in and a "b" to remove. The club has a tool for this but it will not work on well corroded joints. BUT the real problem is that you really need a press to put the new one in securely. This really means stripping the top arm off the car. This is possible with the spring restrained, but a lot of faff. I think Omicron might sell the tool A. If you are just worried about a split rubber gaiter these can be replaced without removing the complete joint.
Thanks. Yes the rubber boot is split and I imagine dirt has gotten in because it makes a grinding noise when I bounce the front end up and down. I can feel and hear it (with a stethoscope) coming from the top joint. I've greased it but it still makes the grinding sound. My car does not have the conventional springs. It has a single composite spring on bronze roller guides put in by a PO.