Help with weight loss?

I'm 5'2" and 190lbs. I am aiming to lose about 50lbs by September, is this doable? A long term goal is to lose 70lbs in total! Also, any suggestions on how to make this endeavor successful? eg. Diet plan, exercise plan, tips on easy and effective weight loss. I'm quite desperate, but I definitely want to do this the healthy way. Please help, i would really really appreciate it! Thank you! :)