I have to say its not a good idea to make global changes on live site.
U may need to install Apache2triad or other server that supports php and mysql then put ur site on ur local machine. Now its safe and more comftorble to edit dezign ur site.
NOTE: u have to config ur configure.php files to work on local machine then u have to upload the allready new web site to ur live host.
tip: u can keep ur old config files from the life server then u dont have to rewrite them :)
All u need to know how to configure configure.php files. (for the database use "localhost").
Import and export database vie phpmyadmin -(there is a lot of threads with this:)
Upload and download vie ftp client such as File Zille or FireFTP CuteFTP etc.
Good Luck
Radoslav



