What some people do is put the home directory on a different partition of the drive. Then you can change or update the OS without affecting home. It may take a bit more drive space and take longer to mount a separate partition when you boot.
I think Mint has LibreOffice included already.
If not, you have the Software Center app on Ubuntu and Mint. It’s like the Windows Microsoft Store: a GUI to browse for installable software.
3rd option is to install it from the command line
Back when I was starting bookstores had basic references from publishers like Reilly’s e.g. Unix in a Nutshell. You want something with a good index that you can find guides for the main utilities.
The good old days used a lot of plain text files so utilities like grep, sed and awk could handle most of the processing. Now I think you’d need more complex tools and their libraries to handle the structured text.
After you buy a train ticket, you push the train the whole way to your destination.