Hi Alex. I also have the GS-1 and have been looking at the Fuji Rangefinders. The number shown is supposed to be the number of rolls. I've heard that when the number gets to 1000 it should be sent to Fuji for service, I don't know if that is a shutter replacement or not. As to the filter, you just have to remember to include that in your exposure calculation. Since they don't have meters, you just meter through the filter first, then put it on the camera.
Paul B.