i selected one of the launchers as my default and I dont want it anymore.....how do i get the option to select another one back
Settings > applications > manage applications. Press the menu button and filter by running if you aren't sure which one you are running currently. Find the one that is running, click on it, and down near the bottom should be a button that says "clear defaults" . Hit it. When you hit the home button you should get asked which launcher to use.
Alternatively you could go to the market and download "home switcher" a free app that can do this.