HELP!?? just starting out

Hi, I'm so glad that I found this site, I really hope someone can help me. My husband and I have been together for four and a half years now, since his boys were 1.8 years and 3 years. He and his first wife were only together until the younger on was about 6 months and the older one was almost two. When we first started out my husband had full physical custody of both boys, the birth mother was very flaky and kind of showed up here and there but never consistently. Ever since a few weeks after my husband and I were dating both boys were calling me mom, and their birth mother by her first name. I am the only real mother they have known, and I love them very much. Now to get to the issue at hand... It has been over a year since the birth mother has had any contact with the boys at all, and I really want to adopt them. We have no idea where she is at, the last phone number we had as hers has been disconnected and we don't know any other way of contact. As far as I know, I needed to fill out forms Adopt-200, Adopt-210, and Adopt-215, in one of these forms it had a place to check that the other parent has not contacted the child in one year and I did. Now I take those papers to the county clerk and wait for a social worker, right??? Or is there something else that I should be filling out??? I cannot afford a lawyer, and I have done all that I know how, any advise would be very much appreciated. Also, it says on a self help law webpage that in step-parent adoptions parents are responsible for any social work investigation up to $700, does anyone know how that really applies and what I might be looking at in forms of costs, other than filing fees.. Sorry so much, but thanks!