The largest name in the business is Grinnell as far as parts and supplies. In this area there are many companies that can do this kind of work--just check the Yellow Pages. My feeling is that unless you are an accomplished plumber, this kind of work is best left to the pro's as it involves a lot of pipe cutting and threading. Also, just figuring your pipe runs on a retro and opening drywall will be major issues. Start with Grinnell Fire Protection and see where that takes you if you still feel qualified.