NVBirthmom,
Welcome to the forums.
In the state of Nevada, an agency licensed to operate there is required to be involved in all adoptions, independent or no. It's possible to minimize your own involvement with them, but you might at least want to talk with them about their counseling services for pbirthparents. The paparents are required to attend parenting classes and have a homestudy done. Normally, the state/DCFS will not release the homestudies they do to private parties, but they should check on it anyway. No matter who handles the adoption, the paparents need to expect that some fees will have to be paid, like the attorney fees, parenting class fees, and homestudy fee, either to have a private one completed, or to have theirs from the state transferred & updated.
If you're pretty sure of a match, then you should first consult an attorney who's experienced in adoption. Unfortunately, I can't offer any suggestions, but the couple you're working with may have some leads.
I hope this is helpful. Please come in and talk whenever you need to.