If it is any of the Aqua Lung (US Divers) double hose you will have no problem getting parts and service. As mentioned above, Bryan at VDH (VintageDoubleHose.com) can help you. He (with the help of a few others) sells all the needed replacement parts.
Bryan is making all the reproduction rubber parts in silicone and even though they look as perfect reproductions, their performance is far superior. The new silicone diaphragms will instantly lower the breathing resistance of any Aqua Lung or Voit DH.
If you are in Indiana you will find several vintage equipment divers in your area that are very active and will be glad to help you get started. As Herman mentioned, DH are great regulators, but they are a bit different than a single hose.
Double hose regulators are a lot of fun to dive (I rarely dive any of single hose anymore), but you will have a lot more fun if you hook up with any of the NAVED (National Association of Vintage Equipment Divers) members.
Have fun.