Move from trial to full version of Aperture 3

I have been using the trial version of Aperture 3 for a week now, and I am really impressed with it. I would like to buy the App version from the App Store. What is the best way of doing this? Do I have to remove the trial version and then purchase and install the App version, or do I just purchase and install the App version and it will overwrite the trial version? I have read a few threads where someone went from the trial to the full version and because of the way then did it, it could not accept updates because it was still being seen as a trial version. I am still new to Apple and not comfortable with the way Macs handle software installation and removal. Any help will be appreciated.