Seconding George's answer - a new signature is required before you resubmit if the 8879 amounts changed. If this is for a 1040 resubmission, you typically need to get a new signature if:

• The total income or AGI changed by more than $50, or
• Total tax, federal withholding, refund, or amount you owe changed by more than $14

Pub. 1345 is where these amounts are from and provides more details.