I know how you feel. My first thought when they told me I had to lose weight was "if I could lose weight I wouldn't be here". But I think they want to test your commitment. And also shrink your liver so that surgery goes better without complications.
After I calmed down, I decided that I would first cut cookies, cakes, pastries, pies and candy out of my diet. The hardest being cake and candy. I continued to eat as usual, except when I wanted something sweet I had strawberries or blueberries with Greek vanilla yogurt, or grapes with Greek yogurt. To my surprise, between my first seminar (February) and meeting the surgeon (May). I had lost 10-1/2 pounds. I was shocked. I even told them there was something wrong with their scales! After that I tried to cut out chips, which took awhile, but finally happened. Just making those changes and not doing anything else helped me lose 25 pounds before my first scheduled surgery. So don't let it scare you. Try some little changes, especially with your trigger foods.
Another thing that helped me was documenting what I ate at MyFitnessPal.com. It helped me cut out some things that I thought weren't so bad, but on the calorie and fat area were off the chart.