Take note the upgrade instructions are all inclusive meaning there are some things in there that may apply to older installs. Also there are things like vblicense which most people if they installed correctly with vb
in the first place its just a note. People on way older installs might be missing certain things in there configs which is why there are notes there. To backup you can use phpmyadmin right in your cpanel webpanel or plesk ensim whatever your host gives you.
For you to upgrade what is important is this
1. backup your database ( that is something you should be doing daily weekly montly unless you want to lose your site ) AutoMySQLBackup | Download AutoMySQLBackup software for free at SourceForge.net
I use this which is simply a server cron task backup and compresses all databases into tar zipped files. You can look at that later use phpmyadmin as noted in my reply for right now.
2. upload all the reviewpost files except the 2 config files
3. run the upload script and select the 4.1 through to 5.1 upgrades