but if you want to learn... and you promise to be careful
depending on your Firefox version you have to look for the files (under your Firefox directory/profile):
- prefs.js and/or all.js ... close firefox... make a backup of those files... look for the "sweetim" in both and just delete the lines... restart firefox and loom again in about:config
if your did it right that would do it... otherwise recover your backups and try again