changing locks is pretty easy. If you take your key to Ford, they can build up a new lock for you to match. I paid £40 for this not long ago.
If you wanna do the whole set it gets tricky when you change the ignition barrel, as the immobiliser (PATS) chip is contained within the key, and will not start if the wrong key is used. It's possible to change the PATS box, but it's a real pain to get to.
Personally if all the other locks are in good order, i'd just get a new drivers side built up to match. The only tool needed to remove/ replace it is a phillips head screwdriver
