Does The PCX have to be 256 colours to make a working unit?
Im soon going to start some unit making if possible but i need the answer to that question Does The PCX have to be 256 colours to make a working unit?

Yes, and you have to make sure the colours in palettes are arranged in right way. Here are somwhere some good tutorials. I suggest read it. It will answer many questions, which you may get, when trying to make a unit.