Adoption is a wonderful thing. People worry about whether the child will be smart, or healthy or normal etc. But the risks are just the same with having a biological child. The world throws curve balls sometimes. But adoption is a fabulous thing for the child no matte what. You are taking a child from a bad situation to a much better one. I have no problem with open adoptions. I have seen many succesful ones. The only rule I tell people to follow, is always tell the child the truth.
No one is ever ready for parenthood. It's always different than the expectation. And it's true, you learn as you go. But good books can really make a difference. Love and patience go a long long long way to making you a great parent. Good luck.