They are replaceable, my local dear repaced mine, and also repaced the sway bar links and steering damper, this was my 92 500 SEL. The upper control arms are not rebuildable, the lowers are. There is a special tool that is used to install them and remove them altho you really dont care since they are throw aways. You must compress the spring, I was scheduled to pick up the car but my serv. advisor called and said one evidently developed a leak in one and they had to replace it. They are hydraulic filled
The PN 140-330-82-07 fr bushing and 140-320-11-89,140-320-12-89 for sway bar links. 6hrs including aignment and new eccentric bolts.
I think it is a bushing kit not just one and you would need two kits (4 bushings) the front is not hydraulic the rear is.