Hoping to adopt. What are we in for?

Hello. Recently, we started the adoption process. We have filled out most of the paperwork and sent in our application to a local and highly recommended non-profit adoption agency. We have been contemplating adoption for a couple of years now. We are not doing this with out lots of thought and discussion. We first looked into international adoption as it seemed more straightforward, however the wait time for the countries we qualify in were/are very long or there are way too many unknowns about the care and the health of the children. We looked into foster care and although we would want for nothing more than a child to be reunited/returned to their birthfamily, it would just be too heartbreaking for us to go through that. Many times its a year or two later when the child is reunited. We are only human and to bond with a child and then to lose them is not anything we can handle. We are in this to adopt not to foster. We had shyed away from domestic adoption thinking that we would not be chosen by a birthmom as we are in our 40s, but then I bumped into an aquientence who is in her 40s with a lovely adopted daughter and she shared her very positive adoption experience and the agency they used. Thus began our process. The adoption will be of a baby. My understanding is that birthmoms contact the agency looking into putting their baby up for adoption. They are provided continued counseling and are not coerced by the agency into adoption. My husband and I want nothing but the best for our children. We have lots of love to give, lots of patience and understand that issues unique to adoption will arise such as feelings of insecurity and abandonment. We will work thourgh these so that they are diabiliting.(I know they do not neccessarily go away, but we do not want them to destroy their self esteem or hold them back from being everything they can be.) We will insist on an open adoption and will stay in touch with the birthmom as much as she lets us (which my understanding is that many cease the communication, not the adoptive parents...maybe its just too painful). We will answer all questions openly and honestly. We will gently encourage age appropriate adoption conversation through life. We will also support and encourage a reunion when over 18yrs old. Also, I should mention that we have a 3 yr old biological daughter. She is a very happy little girl who will be a wonderful big sister. It is partly for her that we will not adopt an older child because we do not want to disrupt the birth order in the family. She needs to be the oldest. I use the words 'adopted' and 'biological' when referring to my children, but they will be referred to as 'my children' in the real world. I do not love anyone more or less because of their DNA. Now that the paperwork is complete and we are awaiting our homestudy, I have started to do more searchs about adoption on the internet, mainly to ready myself for parenting an adopted child. Although I realized that adoption is not natural and therefore issues will be part of it, I did not realize the degree of anger and bitterness that many adoptees seem to have. Understandable, of course. However, I am now frightened. I am frightened that my adopted child not love me/us because we are not the birthparents. I am frightened that he/she will have issues and not let us help. I am frightened that no matter what we do/are, they will never feel like that they belong. I am frightened that they will wish they were never adopted by us. I am frightened that they will resent my biological daughter just because she exists and then maybe she will grow away from him/her and us. I know all children can have some problems. By having children we sign up for that, be it drugs, alcohol, all all kinds of rebellion, but we don't usually think about this when they are a small child or when we are having them. We take it as it comes. But after readign the internet, adoption issues seem to be a sure thing and you can't take it as it comes, because you have to be proactive because its a given....at least that is what I am reading. Right? I know that this is not all about me/us. I know we are the grown ups, but when I hear the feelings, some extreme, of anger and bitterness, I wonder if adoption is ever a positive experience. Many adoptees seem to blame their adoptive parents for being adopted. So I guess my questions are: 1) In your opinion is what I read on the internet the norm or the extreme? 2) How do you honestly feel about your adoptive parents? 3) If there was a biological sibling in the home you adotped into, what was the relationship like? I apologize in advance for such a long and wordy post, but I couldn't find a way to say it more briefly. Thanks and love and peace.