To view skins in MED, simply go to the top in the "view" menu and select "skins". This will bring up the texture viewer/editor. You can import/export images from there. To fix the GXL settings, right-click in the 3D view window and press "GXL Properties" then "Advanced D3D Light Settings". From there, go into "Materials" and play around with the sliders until your model darkens a little or lightens. Keep in mind, if you lighten it too much it will be very bright in your game, regardless of sunlight. Trial and error is the only thing I can suggest here. Play with the figures until you find your setting. If you think you have played too much and stuffed your settings, just hit the "Defaults" button and everything goes back to normal.