1 Not really. It depends on the way the COO is removed. Best way to tell is post some pix of them and the COO collectors can tell you more on what you got
2. warm soap and water cleans them well, but make sure to use a soft toothbrush for the deep down dirt and scrub lightly.
3 http://www.theearthtoymall.com/ best place to pick up supplies and they are cheap.