Newby Question FC4

[chalonec]

I have installed FC4 and am looking for a command line way to search all 
files in all directories and sub-directories on a disk for files that 
contain a certain text string such as the word gateway or mode or any word. 
There are so many config files on Linux that if I had this capability I 
could find out which one had the information I needed so I could then begin 
to identify where I might want to look to fix or troubleshoot something 
other than the log files.  If this were Windows, I would just use the text 
search string gui by right-clicking start.

I have tried find, grep, locate, egrep, man, and the Internet and have had 
varying levels of success but none seem to be consistent.  There are a 
dizzying number of options,

I am pretty sure grep or find should work but I can't figure out how.

Can someone help ?

Thanks,

Roger

(P.S.  I am scheduled for a Linux class next month.)