I am assuming that you want to perform some
sed operation on the contents of each of the files rather than on the list of file names since you seem to know how to do that already. The answer depends in part on the version of
sed you have available. If it supports the
-i option (edit files in place), you could use
xargs again like this:
find . | xargs grep 'userTools' -sl | xargs -L1 sed -i 's/this/that/g'
sed doesn't have the
-i option, you could do this instead:
find . | xargs grep 'userTools' -sl | while read file
sed 's/this/that/g' "$file" > tmpfile
mv tmpfile "$file"