Mine was a brand new installation and the tile guy poked a hole into a PEX line.. So i went to turn off the valve with the big hex nuts that are on the hot and cold side.. nope.. that didn't work.. So you have to turn these weird shaped half moon things that you can't get any tool on. Had to use needle nose pliers. Meanwhile, as you have already imagined, the packing started leaking. The instructions provided were garbage and mislabled which is why we had to do a video chat after the tech support was telling me to turn the thing that I had already done with no effect.
The new rough in valves are different than what Marlinman posted too.. Not sure if theyre improved, but you definately want to know which of the integral shut offs actually shut off and how you will handle them prior to attempting.