To me, the 9th step amends were the highlight of my 12 step recovery program. There were SO many things that I knew I had done to cause harm, and carried so much shame and guilt over them. To be able to look people in the eye, or talk on the phone, write letters, etc, and own up to what I had done, express my regret and then ask what I could do to make it right... I can't express the freedom that it brought.
Be prepared for a look of incredulousness and this person's inability to remember the event. There were a lot of things that I thought were SO huge and imagined this person still carrying a resentment over, and to my surprise, when I made the amends, the person would have no idea what I was even talking about. On the other hand, as IWDO pointed out, they may not offer forgiveness, and that's perfectly okay. You're not responsible for outcomes, just doing the right thing. And it sounds like apologizing would be the right thing to do.