I just Googled "Mongolian Barbeque" and got a number of listings of restaurants around the country -- some are a franchise operation. Either way, I suggest you call the restaurant you visited and ask if they have the nutrition info. Many do -- if you ask.
Stir-frying is a great nutritious and low-cal (if you don't add too much oil) way to cook. You'll find lots of stir-fry cookbooks in the library, bookstores; and recipes online. Many have the nutrition information with each recipe.
Many supermarkets carry hunan, hoisin, soy sauce (even low-sdium) either in the international food section, or in the condiment section (mustard, ketchup, etc.).
Keep us posted!
Pat Baird, MA, RD, registered dietitian