We have purchased a payment method extension for Magento. It is a manual install, and should be relatively straightforward. We will provide the zip file and access to the web server. Care should be taken not to take the website offline or set it in maintenance mode during the installation. This will also require validation that the extension is working as expected. In this case we are installing an extension to allow us to store credit card details for post processing when our primary real time merchant account is not available (brick and mortar solution).