You should only need to send the 1040X form and anything which changed from the original filing.
Please be sure your return is accepted before you amend. If it is rejected, you will be able to add the new information when you make the correction.
It is free to file your amendment, if you need to correct something from your original TurboTax file but you will need to mail in the amendment to the address which will print with the return, as the IRS will not accept them as an e-file.
Here is a TurboTax FAQ with step-by-step instructions for amending your return.