It depends on you as to how much planning you want to do. I suggest that you set a big goal and some small ones. For instance, I want my goal weight to be ___ and to start with I'm going to lose ____ (5% mini-goals, specific weight increments).
Did you know that weight loss is 80% kitchen and 20% exercise? Both of these are important in your journey, so exercising 3 or more times a week will be very helpful to your weight loss AND your overall health. I only do 30 minutes of walking and jogging per session and my weight is still coming down., so 30 minutes, I think, is fine.
As for the food, I have two suggestions. 1) that you don't buy bad food. However, I know that's difficult (I got chocolate this week

). 2) put the bad food to the back of the pantry/fridge and place the healthier options in the way, forcing you to go through an assault course to get to them.
Training yourself to change your food habits will take a few months before you are able to say no and are comfortable around the foods that are your weaknesses. If you do slip, don't be too hard on yourself and remember that everyone does it. Just get back on that horse and keep going
You'll do great!