its not one piece, just grab the bezel around the lens and then grab under the fattest ring on the head and twist. the bezel will unscrew at the first seam from the end. then to install the new module, i used a 1343, just remove the outer spring from the module and then put the module into the battery tube (empty). screw the lens bezel back on until there is no gap and no rattles. insert your batteries and it should be good to go. this is only for the 1343, as its the only module i have.
-ex