Ohhhhhh, yours is right in the front.. I can see why it bothers you so much. I've gotten a number of crowns, but not on any of the front teeth.. that's why I said the temporarily dark gums didn't concern me much.
How long you will feel pain depends on how much trauma there was to the gums and how sensitive your gums are in the first place. I think it is important to distinguish between gum soreness and a true toothache, though. You should expect soreness, but not a major toothache (in my opinion), especially since you already had root canals done.
What I would say is trust your instincts. If days pass and you are not getting better (or feel worse!) don't hesitate to call your dentist. There could be some problem that is easily fixed.
Try not to feel too depressed. I've had all sorts of dental troubles for years, and, while it stinks when you're going through them, everything eventually works out. Your gums will heal nicely, you'll get your nice new crowns, and you'll totally forget about all of this
PS My dentists have always recommended salt water rinses for gum soreness.