First thing is to take a picture of the orientation of the discs for later reference,
Then unscrew the agitator, one side is left hand thread and the other is right hand thread, then remove the disc, then remove all the 6mm bolts and pry apart the two housings you will then have the shaft...
Have one of these collars on my TM 175.
Was on there when I bought the tractor years ago, always wondered was it a new holland part. Would love another one as mine is starting to break up internally now.