To be honest, there isn't much point in a tutorial on building BSG spaceships. To build them, you need to know how to 3d model and texture - not just BSG ships, you need to know how to do that in general. So most tutorials that deal with game modeling and texturing would do. There isn't a magical shortcut that will make you able to build ships for diaspora without going through the motions of becoming a 3d artist first, I'm afraid.. And to do that you need to select your apps of choice, then google any tutorials you can find and get loads and loads of practice. We can only help with specific problems once you already have the basic 3d artist's skill set.