Presently have a portable gas grill with 20-lb tank. Want to connect it to the 100-lb propane tank that also provides fuel for the fireplace. When they placed tank, a fitting was placed on the tank so that the grill could be connected. Have seen hoses for connecting natural gas - can the same hose be used? Is there a way to have a cutoff so that the gas is not always on to the grill?

You can do what you want, not that hard. You can get everything you need from these folks and many others. LP Gas Parts and Accessories (http://www.pplmotorhomes.com/parts/lp-gas-parts-1.htm) They will even talk you through the install