FCABS should be replaced in pairs, just like brakes and struts/shocks. A lot of people, myself included, installed the Meyle HD set. Don't forget to use new bolts on them as well as the Reinforcement plate. A fairly easy DIY. You may need an alignment after installing them. Doesn't hurt to have the alignment checked afterwards.
Done:H&R Sport Springs Koni STR Shocks & Struts, Lower Control arms, FCABs, OFHG, CCV, Cooling Sytem refresh, Coolantsnitch. Yet to do:Transmission fluid & filter, VCG