I wouldn't worry too much about loss of color. If you are worried, you can use cooler water. You can fill your sink full enough to totally submerse the purse, using Dawn or another dishwashing liquid. Before you dunk, note where the trouble spots are so you can give those spots a good scrubbing. If the water turns green, don't worry as you probably won't lose enough dye to make a difference. I have had some purses come out brighter after dunking. You can leave the bag in the water as long or as short as you want but you need to leave it long enough to get soaked all the way through so it will dry evenly. The dirtier it is, the longer you may want to soak it. The dunking will even out the water stains, so that should be much improved. The black mark on the front is from the snap and I think you might have trouble getting that to go away. The scratches will be camouflaged when you apply conditioner. Unlike most everyone else, I don't necessarily think that Blackrocks is the best conditioner for this job. It depends on what it looks like after the bath. If the color is fairly even, then I would prefer to use Leather CPR. It doesn't darken like Blackrocks and you will want to preserve that gorgeous color.
Yes, you would let it dry completely before you condition. Stuff with towels to get it to dry in the perfect shape. You can change the towels once they get soaked to speed the drying.
