Yes, you can edit a published story. Open the story and choose the three dots under your title and on the right after the twitter icon and so on.

Once you’ve made the changes, you’ll need to click the save changes and publish button near the top right of the screen.

Whether you want to do serious editing or not is an open question. Sometimes it’s better to just take lessons learned and apply it to your next story. Old stories get hidden by the timeline and might not get views to make it worth it.

A title change is usually worth doing. Note that you need to change it in two places. Change it in your story but also go to the three dots at the top right and select change display title.