If I have 50 pages that use iRite, can I update 1 using this procedure, keep the WA-iRite folder and have the existing pages continue to work? 
Yes, if you keep the WA_iRite folder, the existing iRite instances should still work.
Another question. I am doing some testing by installing HTML editor under a different user on the same computer for testing. That user did not have iRite installed, but to install on my working user, I have to remove iRite, so how can I Won't it fail to recognize the iRite instance once the extension is removed. HTML editor did not recognize an iRite instance under my testing user.

The iRite instance should be recognized by HTML Editor. Did you have iRite installed before installing HTML Editor on this other user? Also, what operating system and Dreamweaver version are you running?


