For the rear it's very easy. Put the rear on axle stands (let the car rest on the stands, not the axle). Remove both wheels, remove the old dampers and undo the connectingrods to the stabiliser (and, if neccesary loosen the Watts linkage to the rear). This should be enough to lower the rear axle enough to remove the springs without having to compress them. The bumpstops are mounted within the spring, this will come off from the axle too. Remount them by using some soap. Reinstall all the links and install the new dampers. Presto! the car is ready to be put back on it's wheels. I would also change the rubber bushes from the stabilizers and linkages as those play a major role for roadhandling. Here is a thread about replacing the steering rack from the 480-europe forum: