Look up on the DLS for DMU. There are plenty of them up there that are similar to this. You might want to use the Desiro from Siemens. It's a bit more rounded in the front and back, but very similar to what you're looking for.
You must have problems with the textures. Ensure that the textures are uncompressed Targa (TGA) files. If your paint/photo-editing program only produces TGA files without any option to uncompress them, you'll get and actual error in TS2010.
Also ensure that the texture name is the same as the original even though it's for the NJT DMUs.
I had no problem at all reskinning my GP-9s for my route. I simply edited an existing skin.
Good luck, I think you're going in the right direction with these.