I know how I would do it in Photoshop
, But GIMP makes me want to eat a gun so I might not be able to help you.
But, in PS, I would isolate the ship using probably the pen tool, or the lasso tool if you're not comfortable with the pen. Then I would copy just ship and make it as a new layer and then paste that onto whatever background you have in mind.
As for the lettering, I would type the regestry and then individually cut and paste the characters into an arc (there is a tool to place letters on an arc in PS already, but I don't use it for registries as it distorts the whole letter into an arc, where as starship lettering is supposed to be normally proportioned digits that are arranged in the arc form.)
Then, I would take that layer of just the letters and use the various Transform tools to distort it so it looks right on the hull.
Hope that helps!