My dad contacted me today, after 8 years?

I don't know what to do. My dad found me on Facebook & was messaging me. He said he knows he made a mistake, & said that he didn't just decide randomly to contact me. He said he loves me & he thought of me every day since he left. The only reason he waited is because he wanted me to be old enough to understand why he left. He said if I were younger, I would've hated him more for leaving. He left when I was 5. I'm 13 now. Today is also my sister's 12th birthday. He sounded very sincere & I want to give him a 2nd chance. But my Mom, she says I really shouldn't believe him. She said he is just trying to sweet talk us. She says that all he ever told her was 'I changed. I changed.' Blah blah blah. My dad tells me how he was very young, & stupid. & he was selfish when he left. Because he didn't put us kids first, he just left. He said he is sorry for breaking my Moms heart, & for cheating on her. He said he is sorry for getting drunk & angry at us. My dad wants to meet up with him, to meet my stepmom & my 7 other brothers & sisters. One of them is only 1 years old here soon. I kind of want to rekindle our relationship. I'm also afraid of getting hurt, & hurting others. Like my stepdad, he has been here 6 years. Longer than my real dad. He's provided for us, & loved us. My biological dad thanked my stepdad today. He thanked him for taking care of my Mom & us kids when he left. I don't want to hurt my stepdads feelings. But I want to spend time with my real dad. I was about 7 when my stepdad came into my life, & I started calling him dad pretty easily. He was always the father figure in my life. I would like to visit my other family sometime, but my real dad has no parental rights anymore. My stepdad adopted me last year. My biological dad told me today that no matter what, I was still his daughter. His first born. & no last-name change or distance could change that. My mom would let me see my dad if I wanted. I honestly think my real dad is being sincere. Any advice?