Great on you. I changed mine at the main shop at Horne Road & the service was good. I find the main shop at Horne road service is better, staff more knowledgeable. Perhaps those at the PC or IT fairs, some are part timers.
401FS is an earlier model than 401W so I would think the W might be out of stock instead of discontinued. 401W was the newer model of the two (mid-2004) whereas FS was from mid-2002.