I do not believe you can tether with live view on the computer display with Aperture 2 or 3 (I have both), tether support for A2 and A3 are fairly basic. If you want live view, you'll have to get
Nikon Camera Control Pro 2 app, which is a great app and perfect if you want to be able to use live view to view the live image with your computer screen. You can also adjust any setting on the camera through the app. Here is a screen shot with the Nikon app (both live view window and settings window on the right) with my D700:
If you have an iPad or iPhone, you can buy the app
DSLRRemote, connect D700 to computer, connect the iPad/iPhone wirelessly to your computer (via a server software included), and then use the iPad/iPhone as your cordless shooting device with live view support. You just tap on the live view picture on the screen to select where you want to focus, and it will take a photo then saved to your computer.
Here is a taken from the D700 via DSLRemote:
The Nikon app is much more expensive than the DSLRRemote app for iPhone/iPad, but it truly works flawlessly for the professional because every setting on the camera can be adjusted via the computer app. The DSLRemote is a bit more complicated to set up (still very simple), but it allows you the freedom to trigger the shutter anywhere you are, while being abled to view the image live on the iPad/iPhone.