Thanks Paul, that clears up several questions (including the mysterious thread on the end of the roller's axle, visible in the illustrated parts list).
You shouldn't have to buy a $100 puller just for this little job. If you can manage to support the roller with its axle vertical by sliding heavy plates underneath the bearing housing, you can tap on the axle with a punch to ease it out. It all depends on what odd bits of ironmongery you have laying about. Failing that, I think a local mechanic would do it for $50 to $80 per hour, and it should only take ten minutes.
