Just had my 328 in to my mechanic for some other issues and was told my AC compressor is getting ready to go and needs to be replaced. When it kicks on it runs louder than the engine at idle. I usually turn it off when coming to a stop because it is so loud. Suggestions on replacement compressors? Looked into doing it myself but am a little intimidated by the estimate of 3 hours to remove alone. Was also told that compressors are very hard to find by the mechanic. Any truth to this?