Replacing older version of Aperture with newest one.
I purchased my 2011 MacBook Pro used and some software was left on it, mostly iLife stuff. Apparently Aperture was left on it as well and I recently realized that. It's definitely Aperture 3, but I'm not sure which version and I don't know if it's a trial or what, but I want to delete the older version of Aperture and downloaded the newest from the Mac App Store.
I have been playing around with the version on the computer just to make sure I like it, so I do have some photos saved in the current version.
How do I go about getting rid of the older version and upgrading to the newest MAS version? Will a Time Machine backup protect everything? Do I just drag the Aperture icon to the trash, then download the new MAS version? Do I need to export photos first? A little nervous about this as I don't want to lose anything.
Thanks for the help.
MacBook Pro, OS X Mountain Lion (10.8.3), 13-inch, Early 2011