Hunty: on nearly all FWD corollas, the rear shock comes as a sealed unit IE: it has the lower spring seat and the flanges to bolt onto the hub carrier.
On the front, the shock is a replaceable insert, and so is seperate to the lower tube which has the spring seat and flanges on it.
Yes, you will have to remove that large nut to replace the insert and keep the lower tubes with the spring seat and hub flanges. NOTE that the Twin Cam and Single Cam versions are different! (at least on the AE82)
No, its not a hard job once you have spring off. Use somthing like a pipe wrench with care, and it will work. (worked for me any way)