I'm like most of you -- started running in early 40s after never having been athletically inclined. I too was always thin and ate whatever I want, but it started catching up with me, and my fitness level was poor. I was coerced by a friend into joining an 8-week outdoor boot camp class at a local club, just 2 mornings a week. It was tough but after 6 weeks I already felt more fit and strong, so I kept signing up for every session. That was over 2 years ago and I still do it. There were some aches and pains along the way for the first couple of sessions, but I think it's pretty easy to tell when you're injured vs. when your body is just complaining about all of the new activity you're introducing. I felt old and almost arthritic for a while, but it passed.
Running was a fairly prominent part of the class but I was bad at it and gave myself terrible shin splints for the first couple of months. I did a little research, discovered what I was doing wrong and fixed it easily, and that changed everything. I'm not a high-mileage runner but I do it consistently and I enter a ton of races just for fun, mostly 10k. It's a perfect distance for me because the pace isn't as intense as a 5k can be, but it's challenging. I'll probably never win anything, even an age-group award, and that's fine with me!
I was about the same weight as you 3 years ago, but spent 9 months remodeling a house on weekends, and also stopped drinking soda around the same time. The extra weekend activity and better diet took care of the extra 10 pounds I had put on over the years, and it wasn't difficult. I started the boot camp class just after that, and didn't lose any more weight but dropped a full clothing size and felt 100% better overall. I've kept a consistent weight ever since and I don't diet; I just eat sensibly... all things in moderation!
If losing those few pounds and keeping them off is a goal of yours, I'd suggest incorporating other workouts a couple times a week along with your running to keep your body "guessing" and strengthen all muscle groups. Boot camp is my main thing (still just 2x/wk) but I also do a little cycling, hiking, etc. It doesn't have to dominate your life but it does have to be consistent. I used to have the mindset that getting in shape or losing weight was something that had an end point -- you worked on it until you got there, and then you were done. Now I understand it's an ongoing lifestyle change and I can't imagine going back to my out-of-shape self of 3 years ago. Good luck and stick with it!