CVV numbers aren't actually stored anywhere. They are entered at the time of payment to help validate that the card is in hand, but the merchant (Walmart) can't actually store the CVV anywhere in their system. Those are for one-time use for key-entered transactions. Anytime you need to re-enter one to confirm the CVV, the card is just validated on the payment network again, rather than by comparing it to a stored value in the merchant's system.
As Rob said, if the card number and the expiration are the same, the transaction should still go through just fine. There are even a lot of cases where if the number on the card remains the same, and the exp had updated, the transaction would still go through. Those cases depend on the bank that issues the card though, or if the merchant uses a card updater service.
I'd think you should be fine to activate your new card.