I have automatic payments. Will an extension affect that? 

So long as the extension is processed at least two days before your automatic payment withdrawal date, Ford Credit will not process a payment for the monthly payment that you are extending.  Ford Credit will then resume automatic payments with your next payment due - there is no need to take any action.  Note that your next automatic payment will include any invoiced amount, so if there is an extension fee assessed, your next automatic payment will include such fee.