Product review (5 stars): The ease or difficulty of getting the old nut off ...
The ease or difficulty of getting the old nut off your machine is going to come down to the age.  My machine was 10 years-old.  There was so much calcification packed into the shaft around the nut that the spanner wrench method will not work.  And the suggestion that you can get this off with a cold chisel is incorrect.  The nut is not flat.  It is tapered.  No way you can chisel or cut it off.  The method that works is using the 1 11/16 socket on an impact wrench that will put out 500 lbs or more of torque.