I have a Sachs 3 x 7 Torpedo hub that the chain (that goes into the hub) is twisted and bent on. I am also missing the proper washer and long nut that goes on the chain side of the hub as well as the little black plastic push button box that goes on the end of the cable for the threaded piece on the end of the chain to slide into, Are these parts easy to source, and can the the chain and rod (I think that's what the chain goes to inside the hub) be switched out (repaired) by a knowledgable bike repair person? Thanks for any information you can share with me.