If you don't already have this useful tool check it out at http://www.chami.com/html-kit/plugins/info/cmbatchreplace/ enjoy!
If it is a LINUX server use via shell access ********** for fl in *.php; do mv $fl $fl.old sed 's/Searchterm/New term/g' $fl.old > $fl rm -f $fl.old done ************** ************** for fl in *.php; do ^^^^ This would change term in all files in the folder ending in .php Change to suit
Here's a similar search and replace plugin for Wordpress http://thedeadone.net/software/search-and-replace-wordpress-plugin/