Do a search for threads about changing the door handles -- changing the lock cylinder is exactly the same.
Find a thread with pictures showing where the interior door panel has screws and clips.
The only difficult parts are releasing the bezel around the interior door handle and finding the dropped screws when you remove the exterior handle. I suggest a 10mm socket with 4" or longer extension and a dab of the black gooey stuff from the door plastic to hold the nut onto the socket.
I found the following page useful, but it's only available through the WayBack machine
http://web.archive.org/web/200410242...olz4ofus/Camry