Update our Custom WordPress Popular Posts Plugin

The website is currently running an old version of WordPress Popular Posts. The plugin is now on version 4.2.1. The current version we are running (version 3) was originally modified to match our design template, which means we can't update it without overwriting the custom code. We'd like to have this plugin updated to the latest version and configure the layout options so that it matches the current design of our website. We also want to make sure that we can update the plugin in the future, when new versions are available, without overwriting any source code. In addition, we want to be able to set a cutoff date for the oldest stories (based on publish date) it should consider when calculating the most popular posts or have some other method of filtering out specific stories from the results. From the description on the plugin page ([login to view URL]), it appears the latest version allows us to both customize the layout and gives us the ability to adjust the time range. So basically this project requires you to install and configure the latest version of this plugin so that it meets our requirements, or offer a different plugin solution that can.