I wanna upgrade from 4.1.7 to 4.1.8 but I have no clue how to upgrade without touching anything else.
I don't think you should have any trouble going from 4.1.7 to 4.1.8, but everyone's site is a little different so no one can guarantee that you won't. Anyway, there's a "read me" file included with the download, just read it and follow the instructions for upgrading.