I am with you. 40 and fat!
I decided to make my changes almost a year ago now, I started a bit slow as well.
The best thing you can do is to make whatever changes you are compfortable with, and that you can stick to. I found that if I changed my diet first (personally Weight Watchers worked for me), and than once I was comfortable with tracking what I ate, I added exercise a bit at a time. In the past i have tried to go full on change everything right now...and that NEVER works.
Good for you for realizing that there is something you need to do. You will find lots of support here in whatever way you need it.