Lookin' good. Just needs some small greebles to make it really nice. Use some shapes + pillow emboss to put small areas that look like utility covers, etc. The areas marked out for the guns to be equipped are nice. When using embosses... you've gotta keep it subtle, or it looks fake at anything but the perfect angle. I generally do embosses with 15% white, 35% black.
And is that cockpit see-through, or just solid? If it's solid, I'd take a look at some photos of reflective glass, and try to gently emulate the effect (google for some pictures of skyscrapers or buildings, and emulate it with airbrush... don't just clone it- it's a subtle effect). It's a waste of time on see-through stuff, but it works well on solid glass.
Lastly, the font needs to be spiffier. It doesn't look bold enough for it to be on an official vehicle- usually on RL emergency response vehicles, you see Arial, or something very close, because it's easy to read from a long way off.
Overall, though... you've gone from not knowing how to get a skin done at all to making something decent pretty fast