Congratulations! You have already made a great start by getting involved in this SP website and asking for help! Let go of the idea of a "diet", and instead get used to the idea of "lifestyle changes" for long-term fitness success.
Losing weight is simple - you only need to create a caloric deficit. The hard part is actually doing that! You already know to decrease caloric intake with your food choices, and increase caloric burn by adding exercise.
Using tools on this site, you will eventually, and gradually, be able to discover the best ways for you to decrease calories in and calories burned for your age, weight, fitness level, lifestyle, work schedule, and budget.
Suggest you start by finding some physical activity that works for you. It could be pick up basketball, baseball in spring, football in fall, or solo sports like biking, walking/jogging, water skiing in summer, snow skiing in winter (do you live by water and mountains?).
You might join your local YMCA, local fitness club, or gym at a local college or university where you will find classes, coaches, and sporting events.
You might try the Couch to 5K program on that website to give a guide as to how to start walking and move onto jogging.
Suggest you spend time reading these web thread posts with others asking your same questions, and other messages to get ideas on how other people have become successful in weight loss and fitness goals.
With regard to your food choices, figure out where the high fat is coming from in your diet and reduce it. Make small changes that you can live with for the rest of your life. Here are a few examples: Alcohol is loaded with calories. If you drink it regularly, can you cut back on some of it somewhere? Some of those high fat foods would be diary, beef, and pork. If you have pizza a few times a week, can you cut it back to vegetarian pizza once a week, or only have 1-2 servings of it?
Suggest you take the SP quiz "portion control" and find out where you are eating too much. For example one serving of ice cream (my favorite) is only 1/2 cup! I had to quit eating one pint containers in one sitting!
Keep reading, learning and trying new steps. Read success stories of others in these SP pages on this website. Ask questions, and see what others are doing.
The main thing is to start cutting back on your food, and increase your physical activity. Here's to a new life and size in 2013! Best of luck to you!