You need to use a combination of mostly positive and some minor negative reinforcement. When you see her chewing something she shouldn't, tell her "NO!" in a firm voice (you don't have to yell but you can't be wimpy either - you are basically getting her immediate attention so she will learn to understand that she will now get a training session because her behavior needs modifying), immediately but calmly take whatever she is chewing away (no tug o' war or it becomes a game she'll want to play), and immediately give her something appropriate to chew on, being very positive when she chews on that appropriate toy/chew bone/etc ("Good girl", a treat and maybe play with her and that chew toy). You also need to teach her the command to "Drop it" or "Leave it". That will make your job of taking "whatever" away from her much easier. Whenever she does something correctly, give her a little extra-special treat (dogs are food motivated, praise motivation is only for much later in the training). Those extra-special treats are only used for training and must be given immediately and each and every time when correct behavior is displayed by your dog. And remember to start with very SMALL accomplishments at first. A child must first identify a piano, then to touch the key, then to press down on the key to hear the note before being able to play Mozart. Be consistent and be immediate in the minor "discipline" and then in the rewarding for good behavior. You will be surprised how quickly she'll catch on. And proper crate training is essential for when you can't be with her to monitor her during this time as well as for a myriad of situations that may happen in the future. The crate needs to be a good place where she is to go when she feels uncomfortable or stressed. It is not to be used as a punishment. The crate is her place where she goes voluntarily and calmly, not to be locked away from all the good activity. The crate needs to be a better place to be under certain conditions (after she has met the repairman and understands he isn't a threat, her crate is where she'll get something good (peanut butter in a Kong) and will be safe from the scary noise of the repairman's tools. Basically, lots of patience and understanding the old saying that you get more flies with honey than vinegar is the best way to train a dog.
