its really easy to replace, there is a strip running along the 'F' keys with a rivet on the right usually, unclip that, undo screws, slide keyboard out.
Remove the cable that links it to the Mobo.
Offer up new keyboard, attach cable, clip in, screw in etc
Changing a key isnt easy on dells, seems to be no rhyme nor reason to the plastic clips, i took another key off to figure out how it should look, made it all much easier