You will not need to re-file your federal return if nothing is changing on it. That said, all of the state figures start with federal, so your federal return will need to loaded in the software prior to amending your state.
Amended returns have to be printed and filed by mail. It can take up to 12 weeks or longer to process them (depending on your state, it may be sooner). If you are due a larger refund than on your original return, your amended return should only show the difference and you will receive a separate check for it. If you owe money on your amended return, it will show only the new amount owed, you will have to mail a check with the return.
To amend:
https://ttlc.intuit.com/replies/3288565
