What approach should the System Administrator use to enable credit card payments when an Opportunity is Closed Won?

Enabling credit card payments when an Opportunity is Closed Won is best achieved by installing an AppExchange credit card payment package. This option leverages pre-built solutions specifically designed for processing payments, ensuring compliance with payment industry standards such as PCI-DSS. These packages typically come with integrated functionalities that simplify the payment process, automate transactions, and provide necessary security measures to protect sensitive credit card information.

Using a custom solution, such as adding payment detail fields to the Opportunity or creating a Workflow Rule Email Alert, would lack the secure infrastructure required for handling payments. This could expose the organization to potential security risks and compliance issues. Similarly, while building a Visualforce page might offer customization, it would also demand a significant amount of development work to ensure the process is secure and efficient, which is not necessary with specialized payment packages available on AppExchange. Thus, installing a recognized and reliable payment solution is the most effective and safest approach.