Go to http://www.xdsoft.com/explorer/ and have a look at 3D Explorer. You get a 30-days-free trial period, and when I tried it, it converted Truespace COB's to OBJ's, making the necessary OBJ tex maps from the COB without any problems. I'm not a modeller, so I haven't really used it, but I'm sure it will convert 3DS files as well. Good luck.