OK don't panic, your change name certificate will probably be returned with your birth certificate. You will also need to for your bank account, medicare and ATO.
So, when it returns make half a dozen copies take them to the police station or JP and get them certified as true copies. Then you have plenty for future use!
I do this for all my important documents then if anything happens I have spares.
I also need it when I got a cheque in my dead name from the ATO and couldn't deposit it in my bank account as it was to a different name!
Bureaucracy!