Peter, it sounds to me like you really need to get your head around the absolute basics first and so I think Blender might be a little 'in at the deep end.' You need a simple package with a relatively simple interface. Shonner is probably the best to advise on this as he appears to have used every 3D package ever - but I'd recommend Sketchup or Wings 3D - maybe even DAZ (if it's free) to start and do some simple modelling. Don't try and build a super-detailed starship to start. Try something simpler. Even just abstract shapes, just to get used to the tools. Create a sphere or a box and find out how to edit and distort it etc.
Don't worry about a paint package yet, either. You use that for creating textures and surface maps (like normals and specular etc) and that'll come later once you've got the modelling sorted.
In recent years I've taken to painting instead of 3D. A single decent cgi image requires hours and hours of work. Modelling is the easy part - and the part I most enjoy. The real labour intensity comes with mapping and texturing surfaces. It's not enough to just slap on a 'hull panel' texture, it really needs to follow form logically and react to light convincingly (and that's where most renders fall down in my opinion) and that requires some complex shaders and a lot of thought.
After that's in place, then it's a case of lighting and again, it's not enough to just slap on an Ambient Occlusion pass and a main light with ray-traced shadows (and I'm as guilty of that as anyone else). Light has to behave properly and convincingly in order to sell an image.
After six months you have a reasonably good render that most folks will either simply say 'cool.' or nit-pick to death - making you wonder why you bothered.
Alternately I can have the same image painted in about six hours. There's no competition really.
That said, there's a nice, satisfying feeling in seeing a decent render, especially when all of the above come together properly.
Crow