Randy1944,
There are several very competent gunsmiths who often contribute to this Forum who could do the job for you. If your description is correct it sounds like the half cock notch has been broken. To rectify it would need rebuilding the broken area with weld and filing or machining to shape and a new half cock notch cut. It may also need to be heat treated. It's not too difficult a job. However, I would suggest you look for a gunsmith that specialises in old single shot rifles, they will definitely have more experience than most other smiths. I'm sure other Forum members will provide suggestions of whom you should contact. Good luck. 
Harry

Harry,  I want to especially thank you for your quick and detailed suggestions about my questions.  I do appreciate it.  Bill,  Thank you as well for your quick and helpful suggestions also.  My hope for my Sharps is to clean it up (without damaging it) and put it back to original - or close.  I have most of the parts for the Lawrence priming mechanism intact - I think.  I would love to see a large blowup showing all of the parts.  S & S still has some parts available for it.  I have no intentions of actually using it.  I understand that most just insert a cap on the nipple by hand and go that route, and that is what I would do.  S & S also has an original sear available if I need that part.  I am not aware of a gunsmith in my area that has experience on a Sharps Carbine and I don't want it messed up.  Thanks so much for your help.  PS  I also would love to have a blowup showing the different parts and corresponding part numbers and descriptions of the entire 1863 New Model Sharps Carbine.