I have a thin vertical green line that appears on my 9 month old 23'' Apple Display, the line goes away, but has reappeared a couple times. Is there anything I can do, without sending it out? or is this the beginning of the end?

There are loosed contacts between scaler board and flexi-cables, at least those where you have color lines. These cables are glued with anisotropic compound and not such easy to fix, to make it right you shall heat junctions to certain temperature and press the cable down to surface with certain pressure, which is specified for compound used in there - consider as unknown.
The easiest way to get rid of these lines is to press flexi-cables with something like piece of foam rubber.
Disconnect all cables coming from the display to boards, take the chassis off, uscrew metal cover from back side of display to get access to the scaler. Now, if you can, connect display back to boards (you may need to take boards off the chassis) and turn on the monitor. This will help you to find exactly loosed spot. Gently pressing to junctions of flexi-cable to scaler PCB with finger observe the behavior of color lines on the display. Then put there thin piece of foam and fix with metal cover. That will work for awhile.