R.K.
My step-daughter has a Guardian Ad Litem appointed to her. My husband and his daughters mother were never married, and because they were so young at the time of her birth neither parent was not probably able to take care of her. Therefore my mother-in-law has temporary guardianship of her.
So far in my experience, the Guardian Ad Litem has been a good thing. She has interviewed my mother-in-law, my husband and the child's mother. The Guardian Ad Litem has the ability to influence the judge on what she/he believes to be best for the child in question. In my opinion the Guardian Ad Litem is very important. She/He is there to make sure what's right for the child is what happens. In a lot of cases, parents can not agree on visitation, custody, etc. and its very difficult on the child, with a Guardian Ad Litem it makes it a little bit easier.
My husband and I are currently doing what we need to do in order to make his daughter a permanent part of our family. The Guardian Ad Litem has been a tremendous help!
I am not sure what you can do to show that you are a good parent. There are several things that classify a parent as good. My suggestion would be to talk to the Guardian Ad Litem, which I am sure she is going to want to do anyways.
I would not worry about living with your boyfriend, so long as he is a positive influence in your daughters life.
I hope this helps. =)