Springs
Replacing the springs is done in the same way as described when removing the rear axle. Unscrew the shock absorber at the bottom and disconnect the transverse arm extension from the axle. Then lower the rear axle until the spring can be removed.
Install the spring in reverse order.
Pneumatic springs
Air springs are removed and installed in a similar way. Disconnect air ducts beforehand. Remove the two bolts at the top and the nut at the bottom.