Baking textures together!!! HELP!

Ok im exporting a .blend file into a .pmd file, the likes of which dont support more than one texture. My .blend file has both diffuse textures and Normal maps. The diffuse textures are pretty much just color, no significant details, so i want to Bake the normal maps into the diffuse to make one single texture. How do i do this? i tried doing Full Render baking, but it says it cant find an object or image found to bake on. Is Full Render baking the way to go with this? or do i need to do something else?? I’m sure i can figure out the no object/ image problem, but to combine the diffuse and normal map, do i use full render? or is it even possible?