The point Arik made about complexity is a very good one. With very few exceptions all of my models are constructed from either lathed or extruded splines, occasionally with a bit of vertex point tweaking, and in essence are no more complicated than your tower scene. If you can construct a simple tower, you can duplicate it a few times in a rough circle, make a gatehouse, a keep and a few walls and you have a castle. My point is that a "complex" model is usually not complex at all, it's just got a lot of stuff in it. And the methods used to move a spaceship across a scene are identical to the methods used to move a basic sphere.
While on the subject of animation, I really do encourage you to have a look at it. It is far simpler to learn and master than modelling in my opinion, and for me much more rewarding.