I need to take my upper off the lower. It appears that there is a detent though lurking in the small ridge under the ejection port, is anything going to come flying out of there when I go to push the pin out for seperation? Pardin the AR ignorance.

Just push both pins and your good to go, they wont fall out. The upper and lower will split apart with ease.

There's a detent and spring holding both pins in the lower receiver and in the IN position. You may have to tap the pin on a new rifle to get them started out.

-- Chuck