This depends on your activity level. The more active you are the more protein is necessary to maintain muscle. .6gram/pound of body weight is fine for sedentary people, .8g/lb for active, and 1g/lb for very active/ athletes is generally what is recommended.
Yes, eating too much protein CAN make you gain weight. If you are eating more energy than you are expending you will gain. Overall, calorie balance is what matters in the end. Eating less then you expend = weight loss & more = weight gain.