How can I REMOVE iPhone Tethering Hack completely 3G

The following link is where what i used to install the Tethering Hack.
I WANT TO REMOVE IT, COMPLETELY
http://macmegasite.com/node/7173
How can I completely REMOVE the tethering hack from my iPhone, and from iTunes/iMac ???
• Do I have to reinstall OSX in order to regain my default settings in iTunes, and Terminal?
• Since i had to put this (defaults write com.apple.iTunes carrier-testing -bool TRUE) inside the terminal for the hack, can i just edit that?
Somebody Please help. This hack is making my phone unstable, and unreliable.
iPhone 3G, iMac Mac OS X (10.5.7)