HELP! Sister is Pregnant!

Well we are in a very strange situation. I always thought that my sister would be our surrogate, but she got pregnant and had her third child back in Jan. of this year and she decided to tie her tubes, which I completely supported. After that we decided to become foster parents and foster-to-adopt. Well, they didn't tie her tubes when she delivered (naturally). She went this AM to get them tied, they gave her a pee stick, and GUESS WHAT! She's pregnant! Obviously, this is her worst nightmare come true. She is with her child's father (also the same father of her former 3 children, and one aborted child). After she had my niece, now 4, she got pregnant quickly and had an abortion. That is a decision that has been very difficult for both her and her boyfriend to handle. So they want us to adopt this baby! There are obviously many legalities involved, and I don't even know where to start. I am flying down this weeked (pre-planned trip) to visit them, and then we are planning for them to come up in July to discuss everything in person. Any advice is GREATLY appreciated. I'm not getting my hopes up, she wouldn't be due until Jan. 2011, but I am cautiously optimistic about the thought of being a mom!