Where to start

My biggest suggestions would be to make changes graudally. Often times when people are trying to make huge changes in lifestyle (this definitely includes eating) they begin too fast and get frustrated or burnt out and don't continue on with this plan that they have. So if you are not used to eating a certain way start with subsituting two things you would normally eat, such as a candy bar and regular soda with water and a fruit. Then the next week continue subsituting things that are probably not the healthiest or best choices until you are at your goal. This I find is really what help people stick with it and not feel overwhelmed by changing everything they eat, or feel like they are giving up everything they love all at once!

Secondly while I totally understand wanting to lose all that weight 50 pounds in the remaining time you have (until mid-June) would require just over 4 lbs a week which really is not healthy for you body. I would suggest you set your goal at around 24 pounds which is a challenging but healthy 2 lbs a week!

How much are you exercising now? This goes right along with food, try to increase this over time as to not overwhelm yourself with a huge amount of time working out! If you are not currently working out start with 30 minutes a day doing 20 minutes walking and 10 minutes doing some weight lifting. (You can find great workouts online!) Then over time, depending on your schedule, continue to add 5 or 10 minutes a week changing up your workout routine and adding new activities. Soon you will be burning lots of calories and making changes that will really last a lifetime!

Good luck and stick with it!