The National Center for Transgender Equality has a webpage dedicated solely to helping you navigate the myriad processes and procedures for all sorts of documents you may need to get changed. While just limited to the US states and federal level of documents, we are looking for those same resources for other countries. Please bookmark this weblink as you start the document change process: https://transequality.org/documents.
And if you have questions, or something seems confusing, please feel free to PM me. I'm the liaison with the National Center for Transgender Equality here on TGH. I will do my best to help you out. Hugs, Michelle