Cheryl, you weigh about the same as me. I ran every day for 10 years when I was slim, but I'm so embarrassed to run outside now.
Stupid, I know.
However, I'm joining a running group next week. It's part of my weight loss clinic, so it'll be all chubbies running.
I know you'll get some great advice here, but I'd recommend a run/walk program to start with.
Warm up, walk for about five minutes, then run one minute, walk two. For 20 or 30 minutes total, or whatever you're good for.
I know there are some links on the Internet to those kind of programs... I'll see if I can find one if you're interested. I tried one from Prevention magazine a few years ago.
As for the treadmill... I have one, and I do find the impact of running on it as opposed to hard ground less of a stress on my body. Particularly at my weight.
Congratulations on your weight loss, btw!! 55 pounds is AWESOME!!