Montana,
If you look at any of the carrier shots you'll see that the flight decks aren't a single tone. The non-skid surface is not put down all at once, but in sections, so even on a new carrier, the shades of gray will differ as the dark gray fades under the sunlight. The deck stripes maybe fresh over several different gray tones.
Gunship gray is isn't a bad start at all. That sea blue color will dry out too blue, I believe. You could use it on the hanger deck surface, if you'd like. Look at several overhead carrier shots and you'll see even, straight edges where the non-skid application stopped and then was started later. Using the photos as a guide you can do a subtle mix of gunship gray and a little black, for "newer" areas and then mix in light gray for more worn locations.
Once the decals, or painted stripes are on, you can weather the deck with washes, dry-brushing, chawlks, whatever method you choose.
Aircraft carrier flight decks are dirty places. Check some other Navy shots and see how dirty the sailors' uniforms are.
Depending on how long the ship's been at sea, you'll notice weathering in some rather standard locations, too. A brownish/black grease color quickly fills the flight deck elevator tracks and often leaks to the hull. The top deck on the island can often weather to a grayish tan color. Again, just check your reference photos.
Many ships will have a grayish-black sooty color on the port forward side of the island. Most of the time the E-2C Hawkeyes are parked there and their turbo prop engine exhaust discolors the paint when they are started. This would be pretty subtle in scale, but it is often there.
You may want to rent the movie, The Final Countdown. It has been recently re-released on DVD. It was filmed in '78-'79 aboard the Nimitz and your model is very close to the ship's appearance in the film.
Enjoy,
Mike