A shop that cares about how they do shit will often have a spring compressor that squashes it down and un does the nut from the shaft. The manual back yard garage way is to compress it yourself w/spring compressors, hold the shaft w/the right size open end wrench or allen key while you spin the nut off. I am willing to bet that the place you allowed to lower you car held the shaft in place w/some vice grips to keep it from spinning while they un-did the nut. That in turn burred the shaft and cut the strut seal.