Sure! The easiest thing is go to the Dates tab of the booking and change them. If you haven't changed the charges from the default charges, you can recalculate them at that point. Or if you have changed the charges, once the dates change is made go to the Charges tab of the booking and update the charges to match.
Then go to the Transactions tab of the booking and make sure the payments are what you want. If the guest checked out on a quote, you'll have a default scheduled payment for the final payment for remaining balance, so that would automatically pick up the new balance. Or if you need to charge now, you can charge the card if you have a card on file or request payment if you want to let the guest do it (or they're using PayPal).
