One of the common problems with scaling in Blender is its important to keep the object scale = 1 - meaning it is not scaled.
Check out the screenshot.
I don't know why, but, being scaled causes problems in Blender's own game engine as well as the exporters. It is best to do all your scaling, stretching and whatnot in edit mode.
When I export a format for Java the model in the picture is huge and have to scale it down, but other formats it is very small and have to scale it up.
Blender has very good UV-mapping, but can be a little tricky to say the least. In this model, I am using 2 materials that have different levels of specularity, but, for the x format I only need 1. The textures need to be in the same location as the x file for this model, but I think it goes by the file paths relative to your .blend file.