You have to push the thumb wheel downward to switch from Apeture to Shutter speed and the turn the dial to what you want. It is very easy to bump the settings off just by carryng it around or while shooting. Also it is very hard to see what you have it set on just looking at the LCD. The numbers are small and in bright light very hard to see. I hated that. I am much happier with the two thumb wheels at the top on the 7 and the EVF to read the settings .But still with that it is easy to knock it out of whack. You can lock the dial on the 7 with the push of a button. You will be very happy with the IQ of the NEX 3 or 5 but the 7 smokes both of them on higher ISOs. I missed a lot of shots with the NEX 3 and 5n. The NEX7 is a much better over all camera with the built in finder. IMO.
You could always get the finder for the 5n but with that the controls are still going to be a PITA and the finder easily damaged setting on top like a setting duck.