Hey there, welcome to 3fc! Adding in the walking is definitely a step in the right direction. If you keep up with the 1.5 miles, and have the desire to, eventually you'll build up to being able to walk more, which always makes me feel great, personally.
If you're wanting to do other sorts of exercise, definitely talk to your doctor or a physical therapist to see what sorts would be okay for you to do, given your past back surgery.
As for the food, it's really a personal thing, and very much about trial and error. When I first started trying to lose weight, I just took a few things out of my diet. Soda pop, fried foods, candy bars, all gone. That helped to cut down on calories, even though I wasn't counting calories at the time, and the weight started going down. I calorie count now, and there's loads of different online calorie counters that you can use to figure out about how many calories you should be consuming. Definitely check out the forums here with the various types of diet-- calorie counting, carb counting, meal delivery, etc. You'll find something that works for you.