Typically when I do an upgrade of the php code I rename my web/moodle directory to web/moodle144 and then create a new web/moodle directory where I put the new files. That way, with a good backup of the
database you can easily switch back. I think what the instructions are trying to avoid is that you get some old code (depracated files) and some new code. I hope this helps and want to encourage you to keep at it - one step at a time.