Hey, I am an adoptee. Like you I had more information than most do regarding bparents and my adoption. I had first name and maiden name of bmom as well as 2 different married names (she had married twice and divorced). I knew what state I was adopted out of and what town. As far as bdad, I just had first and middle name, no last name. With the information I had, I first contacted the hospital I was born at and got all of my birth records. I am not sure how that will work with you being you've had this info for 20 years. My best suggestion, something that helped me quite a bit is to use a search angel if you haven't already. They are free (something I was grateful for seeing as money is tight here.) Here is the link to the search angel group that I worked with, MIRACLE WORKERS I tell ya!
http://www.aci.net/schaefer/page60.html
Good Luck. I am happy to help if there is anything I can do. If you want, feel free to pm me any information you might have and I can see what I come up with.