Tom The "offending" piece looks very much like the two pieces in the middle of the picture for the Dexter E-Z Lube Spindle Nut Kit #K71-622-00.
Scamp has just given me the Dexter website (which is helpful) but all it says re: removing the hub is that "For E-Z Lube axles produced after February 2002, a new type of retainer is used. Gently pry off retainer from the nut and set aside." So I guess I'll try to pry off gently (as Darwin suggests) and plan on buying a new set before re-installing everything. Thanks for all the help, and I'm sure glad I started looking into this now instead of when I want to head off in the Scamp!