2 pieces of advice...
when it comes to reforming diet, slow and steady also applies. every few weeks, pick a new food to replace with a healthier alternative and over time your tastes will adjust. once it becomes second nature, it will be "the norm" and you wont have to think twice about it.
when determining target weight, body fat percentage is a much more insightful indicator of health than only body weight. you can get an analyzer (or even a scale that has one built in) at most department stores. they arent super accurate, but they will help you chart your relative progress better than weight.
BMI is pretty much useless
oh, and great idea with the accountability thing! you should also tell a few close friends so it's not as easy to give up.