I have no idea how to create Minecraft mods but would be rather interested in learning how to but I want to start with something simplistic such as improving the Minecraft map a little bit. Over time I found myself disliking journey map and wanted an alternative because journey map started to feel quite cheaty to me. I wanted to know how hard that would be. I am not quite sure what I want to rework entirely yet but something I would like to do is add coordinates to the map. How hard would something like that be to implement? Thank you.

How hard something is depends on your experience and your skills. But if you have no experience with modding at all, custom map displays may not be a good place to start. They depend on the interaction between many classes to display properly (ItemMap, MapData, ItemRenderer, and MapItemRenderer), so it's not as simple as just rendering some text.

If you look at this topic you''ll see Major Squirrel tried doing something similar, and was only able to make it work with lots of copypasta and spaghetti code. So without modding experience, I would suggest you save this project for later and start with something smaller. (I know it may seem small in theory, but maps are unique in how they render, so it's not really as simple as it sounds.)