Hi folks.
For the style question, I have this answer:
1 - Open the Style Window. Normally the Select tab shall be selected.
2 - Choose the "In model" Styles (the small house).
3 - Click on the Edit tab.
4 - Click on the third icon.
5 - Click on the square to the rigth of "Background".
6 - Check that you have RGB to the right of "Picker", if not, use the pull down list to select RGB.
7 - Slide all three cursors to 0 to get pure black.
8 - Click OK then Update the style.
9 - Hide the axes and you are done.
For the stars, however, you would need to add some small dots or small geometries, using different colors since stars comes in all kind of colors or, better yet, use what was suggested, using a watermark made from a nice sky photos. There are now so many nice photos available on the web.
Good luck with your project. This is one things I already though of modeling, the Rama spaceship, outiside and inside. Using the extremely precise description of A. C. Clarke, it should not be too difficult.
Have you read all the four books of this saga ?
See this :
http://sketchup.google.com/3dwarehouse/details?mid=c3239ab7c577d245298d8588f7bc19ff
By the way, since the ship is 54 km long, SU migth have clipping problem with such a large model if you draw it at a 1:1 scale. I would try using a 1:10 scale. But, try it as you whish since you can use the Scale Tool to adjust the size at any stage in the modeling process. You could even use a 1:1000 scale, using meters but pretending that they are kilometers.
Just ideas.