Go to the library and get practically any dog training book - everyone has their favorite, but the good thing about the public library that it is free to check out several books and see which one appeals to you, whether its the Monks of New Skeete, Cesar Milan, or whomever.

You need to set time aside every day to work on training her, start with basic obedience, like she was a new puppy. Work on leash training, staying calm, and not tugging when she is on the leash. When she is perfectly behaved on the leash, then you can try the dog park, maybe early or late in the day when there are not a lot of other dogs there. Keep her on the leash, and constantly make her pay attention to you. As soon as she starts acting up, "sit" and "down" and "stay" until she is calm again. You may feel silly, but she seems to need to relearn who is in charge - and that's you!