A little more changes to SignOn Manager, and I now have options to change you username, password and login options through the userscripts menu. There still seems to be some problems with GM_registerMenuCommand that I am trying to resolve. This removes the problem of the infinate loop if you save a wrong username/password combination in the script that I wrote.
During this, I also added the implementation of the GM_xmlhttpRequest function to the greasemonkey development framework that I was writing. I need to test it out. In the meanwhile, if you have suggestions, please do ping me.