I'm not that much of a programmer but I'm pretty good at finding pieces of code online and meshing them together to get them to do what I want. I've already set up a basic Shopify App that displays information and I've installed it on a development store using this guide https://shopify.dev/tutorials/build-a-shopify-app-with-node-and-react
best way to start is to look at the docs on shopify.dev
The docs are pretty extensive. But basically what you want to do is when the app installs, access each one of those specific files using the Admin API and the Themes endpoint. https://shopify.dev/docs/admin-api/rest/reference/online-store/asset
Each of the liquid files are Assets. So just look up each one and make the changes to the value. Pretty easy!