How long does it take for plaque to build up in arteries and is there a way to test for it?

Depends on diet : Arterial plaque has been found at autopsy of gang members (teenagers) and in deceased soldiers. The "western" diet (watch "supersize me" for more info) speeds deposition, while mediterranean & others slow it. Family history and cholesterol levels (if very high) can also contribute. Certain ultrasound studies of the blood vessels can screen for it. Ask your doctor if concerned.