I'm not good with texturing in sketch up,but what I notice that Google Shetch Up 6 had terrible 3DS exporter,so I use Sketch Up 5,give much better and quality export...don't know maybe that's one peace of exporting problem.
One more thing,some model part could be transparent after exporting,it's beacuse you need to all out faces been proper turn,when you create box or any shape make shure that are faces turn properly.