ok, if you are wanting to know how you can find and replace text in a file in linux you are in luck, i will show you how..

lets say i have a file called wallpaperama.txt and this is what the files has:

Wallpaperama is an amazing collection of high resolution quality free wallpapers.
you can download your favorite wallpaper for free.
tell your friends about walllpaperama
you can vote for your favorite wallpaper
surf with confidence, all our wallpaper dont have spyware.
we hate spam, so we wouldn't give you that either.
we hope you enjoy our beautiful wallpapers


ok, on the example text file above, lets say i want to change all the 'wallpaper' to 'screensaver' well this is how you would do it..

lets assume that wallpaperama.txt is located on my home directory at: /home/me/wallpaperama.txt

step 1. open the file with the vi editor:
vi /home/me/wallpaperama.txt

step 2. Enter - SHIFT + : (the Shift key and the colon key at the same time) on your keyboard, the screen will look like this:
20080904_6332_vi-editor.jpg

step 3. now enter this command and hit enter
:%s/wallpaper/screensaver/g


step 4. now you will see that all the text 'wallpaper' was changed to 'screensaver'
20080904_6332_vi-linux-editor.jpg

step 5. save the change with this command:
:qw


DONE

i hope this helps you