Basic tutorial/ QA is the first post of this thread.
That error means that you have a material assigned that does not have ED's custom assignments to it. It might not appear in the material editor depending how you created your model, but using the sucker tool in the material editor, select your mesh if you know which one is bad and it will appear.
A1: To correct textures: Textures need to have a special material type assigned to them. This is done by opening the Material Editor (M key). Select your texture slot. Then click on Utilities, EDModelTool, then click "Make Cool". If you do not see EDModelTool, Click 'More' in the Utilities tab and select it. Back in the Material Editor, you will now see a new category called "Material Attributes". For most items, use "Default" in the pull down section. Do this for each material slot and export normally.