My mom is getting married again

My mom and her new boyfriend whom she met from joining dating tours are planning to get married. As much as I want to be happy for my mom, I’m having mixed feelings about this thing. I’m used to my mom dating around but she never really reached the point of wanting to be married again after her divorce with my dad. I’m not really sure if I’m ready to welcome a new member in our family. He’ll be living with us or maybe, we’ll have to move in with him and that’s not something I really want to do. I just think that so many changes will have to take place and I’m having a hard time taking those thoughts in. I’m also not sure if I should open up to my mom. I’ve only told my best friend about these things. I’m not exactly sure what I should do at this point. Any suggestions guys?