Okay I need some advice here everyone WELCOME!!!!

This is really a tough one. I would say give him a chance at redemption. But I think he should hear that you have things to get off your chest like how you were feeling so hurt over his having abandoned you for all those years. I would put all those feelings into a letter because verbal exchanges like this can too easily become inflamatory and confrontational. Then wait a couple days or so if he wants to discuss the content of your letter.

A person can only be changed by him/herself. And in this case maybe he has taken the initiative to bring change within himself. But until you know for sure, I wouldn't raise my hopes or expectations too high.
I wish you the best in this. --Lydia

Maybe this seems so stressful because it revives some unpleasant memories that were buried in the past. But ultimately this will probably be a cathartic experience.

You might mention a lot of the experiences you had growing up where you missed his participation. He wasn't there, for example to teach or to observe you the first time you rode a bike, roller skated, climbed the stairs, etc. He missed observing you heading off for your first day of school. He missed seeing all the things you took pride in doing when you were a child, etc. And he just wasn't around to provide all the paternal support and guidance that fathers are supposed to provide for their children. How did you feel when you would see your friends with their fathers? Maybe you can tell him that made you feel hurt, left out, deprived, etc. I think this is likely to be most effective if you just describe your feelings without being judgemental or accusatory.

Anyway, just some thoughts. Hope this is in some way helpful. --Lydia