Any good training begins with two receptive minds. The best state of mind for absorbing information is a calm one. To open the door of communication with your dog she has to be calm and attentive! Here is a Kikopup video
on how to "Capture Calmness" which includes training the "Default Behavior." A dog feels a lot more secure when she knows she has a "Default Behavior" that will always please you when you run into road blocks with training. Also, giving her a good long walk before training helps ease her mind and gives her an advantage when training "calm."
I would suggest training these first before obedience stuff. This way you'll lay good communication groundwork to help guide you both during training the more complex and time consuming behaviors ("Sit", "Lay Down", "Stay")
As for the barking, there's a book I always recommend to people with Chihuahuas because their reactions to the world are very different than a larger dog, so our reactions must be coherent with theirs in keeping with their size and sensitivity!
The author of this book writes that with Pogo (one of three of her Papillions) she will remove him bodily from the situation that is causing him to "over alert" or "over excite" himself. Her example is squirrels at the window. When Pogo starts bouncing and screaming she will pick him up and put him in her lap, which teaches him that the more excited he is, the further away he gets from the squirrels. As soon as he's quiet again, he can get down and go look at the squirrels again.
It's a great book, only 1 cent on Amazon!
Hope this helped! Training is so much fun, a great way to bond, but it sure can feel frustrating sometimes! Good luck and keep us updated!