The thing I didn't count on after dd#2 was born was the guilt. What a total shocker. I felt like I had taken something really important away from dd#1 (100% of my attention) and that was so hard. I felt just awful, like I had made a huge mistake by having another child. It was also hard to watch dd#1 "process" what was going on - I could almost feel her hurt - that nearly killed me.
However, it's been two months now, and I am so happy with my two girls. DD#1 has coped very well...after the first couple of weeks, she was petting dd#2 telling her she loved her, that she was a "soft baby sister". Now she calls her by name, tells her "good morning", "good night", gives her lots of kisses and hugs, and seems back to her old self.
Just remember: your two children will grow up loving and caring for one another. They will share a very special bond. Remembering this helped me get through the guilt I had. There will come a time when they don't really need me like they do now, but they will need each other!
Sometimes I still feel a little guilty when I can't get to dd#1 as soon as possible when she falls or needs a diaper change, but in the end it all works out and I believe that my girls will know that I love them both equally.
The other posters are right...try to get dc#1 involved with diaper changes, etc. Good luck to you!