94 taurus tranni problems

I have a 94 ford taurus with the 3.0 emgine, and a tranni that now only has 1st gear and reverse. I am trying to get a used on from the salvage yard, but I am not sure if it is a axod, a ax4s, or a ax4n. Could someone please help me! Does it even matter wich one i get, and what are the differences. Does anyone know what might have caused the problem either