For the bookings accepted through Vrbo, my rental contract requires the guest to make their second payment through my OwenrRez/Strip account rather than on the Vrbo platform. When requesting the guest submit a credit card the only option I can find is the one to submit a "new" card. The header reads "This page will help you update your billing information so that future payments and security deposits use a new credit card instead of the one on file. Use the fields below to enter a new credit card and select what types of transactions it should be used for." Is it possible to change this heading or am I missing an option to request CC info without requesting payment? The guest does not have a CC on file as they made the initial payment through Vrbo.
You're misunderstanding the message. Requesting the guest's credit card this way, will do exactly what you want - it'll store their information for future use, and then when the scheduled transaction time arrives, it'll use it to make the payment. Not before.
My guest needs to update her Credit Card. Where can I find this link or request?
Go to the Booking in OwnerRez, Transactions tab, and use the Request dropdown button to Request New Credit Card. That'll send the guest an email with a link to enter the new card information, which will then be stored in the Booking record available for use.