The advice you get here will vary and you will need to decide what is best for you. All the advice are not based on good evidence but each will say that their advice is based on good evidence and personal experience. So this is my advice.
You are right to be concerned about your weight, specially at your age. That is a good start.
No amount of exercise will get rid of that much of weight and get you to a healthy weight without changing your current eating habits.
What I advice is not a diet or meal plan but what I call healthy eating. This is because what you are trying to achieve is not a target weight and then forget all about it. You need to stay healthy for the rest of your life. Therefore it has to be sustainable. For example, I meet people who had given up all sweets and sugar but craving for it. What I suggest is eat in moderation. For example, biscuits and chocolates used to be treats that we used to have occasionally. Not whole packet every day.
Then combine it with regular exercise. I emphasise, regular. It is not doing too much that you are too knackered to do anything for few more days.
I recently cycled Route 66 with a group of Americans. I am in my early 50s and I was the youngest in the group. The next youngest was 60 and the oldest was 74. The majority were in mid 60s. They all have one thing in common. They have never been on a diet but they all eat sensibly. They all cycle for fun and none have been or on a training regime. I had exactly the same experience when I cycled in Russia in the summer. The oldest in that group was 80. For all of us, it is just life style.
No special diets or training regimes.