This is one thing I haven't done.... does this mean I'll lose all my settings/work that's currently saved? and how do I go about doing this?
Against what @malikkamran says.
If you do a proper full reinstall of booting into internet recovery, cleaning the hard drive (Erasing it) and then reinstalling MacOS to do a completely fresh install then yes, youll loose all settings
Back up everything onto an external hard drive and then copy back on after reinstalling MacOS