I think that both Steve and Jon experienced serious changes. The only difference is that Steve changed as a result of getting to know Jon, while Jon changed on his own will. Jon took it upon himself to change, even when nobody expected him to change. He was going to die and nothing he could do was going to change that, which speaks a lot for his remorse and his character. It is that character that showed Steve that anybody can turn their life around if they really want to, which could have been what helped get Steve clean.
I also think that this story says a lot about our correctional system, and its unwillingness to change. Steve mentions it briefly at the end of the story, but what he says is very profound and insightful. And I think that this story shows that one man can make a difference, but only if people are willing to accept the change. By that I mean if people do not want to see the change they won't, and Steve is showing that someone that does something horrific can change and that nobody is beyond rehabilitation if they want to be rehabilitated.