Stick with the orange dress, it will be a bold statement, I love it! And def no tanning, your dark hair and light skin will make it even more amazing!
However, skip doing any color on your nails. Orange is amazing on it's own and adding any other colors to your look is going to make it clashy. Get a mani/pedi and just do a nice clear lacquer on all your nails.
Shoes - strappy, open toe. Don't wear closed toed or chunky heels. And don't do orange, like you said, it will be orange overkill, we want the dress to be your shining glory. A sparkly silver or gold would be perfect, depending on jewelry you are wearing. Again, with such a great outspoken dress, less is more on the jewelry front too.
Straight iron your hair and find a super cute girly clip with orange in it (like a butterfly, flower, etc.) do a side part & put the clip on the side with less hair (does that make sense?) and let the other side fall naturally, it will look fantastic.
Makeup- play up your eyes, do smokey eyes with neutral and dark brown shadows/liner. No black, we want to stray away from using black with the orange. Just internet search "smokey brown eye shadow" if you need help/ideas. Use a blush with more brown tone (not peach or pink) and blush from the back to the front, just under your cheekbone (practice this a few times if need be) and then a simple light lip gloss (Cover Girl Wet Slicks in Sugar Maple would be perfect!)
Love it when guys do the white tux, but he should have the personality to go with it, it's pretty bold. Otherwise a very dark brown tux with orange accents to go with your dress, no black, we don't want the whole halloweenish black & orange thing.
Then just be confident because confidence is what makes a woman truly gorgeous! Have a great time!