Replace all the springs with a fresh set. Aside from that, among the small parts there's nothing breakage-prone that isn't already commercially available (firing pin, extractor, etc.). As a collector I keep a small number of vintage parts on hand, but that is mostly to restore any new aquisition to its correct status. For example, I recently bought a nice WB Colt that was correct except for having a WW1 slide stop. Fortunately I already had a WW2 Colt slide stop in my parts box.