New York Birth Cert.

I am helping a friend find her bparents. She was adopted at the age of 3 and her bcertificate was amended at the age of 4 1/2. It could be possible that she was with at least her bmom until she was 3. Is it possible to go to the town where she was born and try to get her original bcertificate if I don't tell them what we're there for? I've also read something about a birth index. What would that be and is it accesible and will it tell us anything? I want to make a trip to the town clerk but I don't want to mess it up and not find anything. Thanks for any help.