There's not much you can do about the zipper except replace it. The MOST professional way to add the panels and the detailing would be to take the jacket apart and add trim and new panels to the side, but you could also achieve a decent effect with carefully applied bias tape to the arm seams, and applique on the sides to create the white panels. If you use fleece for the applique, you also don't have to worry about hemming the pieces, or using a satin stitch, and that will cut down on time while matching your vest fabric. I wouldn't go with paint, since it will probably mat down the fleece of the jacket, and look obviously like paint.
Hopefully this came in time to help with your rush!
"Not a word."