I would have done:

then you get a pop-up box asking for root's password. I usually use kwrite, but it should be the same for kedit.

I usually use nano in a root shell prompt to edit files.
Sometimes I don't like to work as root and I'll make a copy of a file I want to modify and then I'll make changes to the copy as a regular user. When I'm finished editing then I'll su to root and copy the file into the proper place.
Let us say you wanted to make changes to inittab. You could make a copy of that and place it in a directory (documents). As a regular user navigate to your directory and use kedit or kwrite to make changes to the copy then save. Then open up a shell prompt, su to root.

# cd /home/hitest/documents
# cp inittab /etc

I also like to back-up files before I change them.