You ever think about using Blender? Its Free and amazing! I use it all the time when I am not playing WT and working on other projects. I introduced my son to blender when he was 14 ,he is 16 now and loves it. I tried out sketchup when it first came out ,its not bad.
If you are looking to get started with blender you could do worse then heading out to http://cgcookie.com/blender for some tutorials. Yeah there is some pay to view stuff there but a) it’s cheap and b) plenty of free stuff to get started.
^^ lol you would not bleave how long it took me to learn SketchUp. (i started when i was 11 yrs old)
I can see you making 3D animation later on in your life. When you get into a school and with some sort of school E-mail. Look up autodesk 3Ds max or Maya. that software is from the same people that make auto CAD and you can get that software as a student edition for free.
With that software, you can put in your work into some kind of game engine. granted, there are more steps to learn to do that. but from what you know already. you should be able to apply that knowledge from Sketchup and make your own ships.