But I think you cant use the path using sed
Why do you say that? You can put anything you want in the SED syntax. Do mean path in the "s" command, or the path in the filename? (In this context, I suspect the latter)
Note that--regardless of where used--pathnames need to be in one of two forms:
1. Relative to the current position
2. Absolute, starting with "/"
Maybe I should be using grep though.
GREP doesn't do find and replace....
I would go to http://tldp.org
and get the Bash Guide for Beginners. Also, some excellent tutorials here: http://www.grymoire.com/Unix/