Got the hood open. What an ordeal and we were ready to give up on it. The thing that caused the cable to fail was the pin that connects the cable to the release mechanism went away. Where it went is anybody's guess. It was simply gone. That was actually the good news, since had the pin been in place and the cable itself was broken off under the hood, this would not have been resolvable the way we eventually resolved it - which took hours.
Ultimately, we took off the grill surround. Fortunately we did not have to take off the little black louvered pieces behind the grill since to do that from the outside would have been even more time consuming, if not impossible.
The next step was to remove the hood hinges from the hood itself, not from the car. This does not give you as much freedom of movement as hoped and you have to be REALLY careful to not bend the hood at the attachment point where the hood release is holding onto the hood itself.
This allowed us to have one single inch of visibility to look into the hood at where the latch mechanism is. This is very little room to accomplish what we ultimately had to accomplish. Since the connector pin was missing, we were able to see into the hole into which the pin was supposed to go, through which it would be connected to the cable. The game plan was to try to figure out a way to get something into that hole in order to move the release mechanism to the right which should pop the hood. One of the complicating factors is that the tube that houses the "pop" spring mechanism is in the way of direct line of sight with the hole into which we ultimately had to insert the tip of our improvised tool. Without boring anybody with all of the sordid details, we eventually came up with a long piece of very rigid metal circular rod. It has to be rigid enough to not bend when pressure is applied to it, and given the length of the rod this was no small feat. We ultimately used a piece of rolled steel rod approximately five feet long, 5/16" in diameter, with an end ground down to be small enough to be inserted into the release lever hole.
Then the tedium began in earnest. Trying to find a fulcrum point where we could use the rod as a lever was very tiresome. This was compounded by the fact that the end of the release cable was still inside the mounting bracket for the release mechanism. Because of its positioning, we could only move the the release mechanism so far to the right before the travel was blocked but the release cable. Ultimately we had to try rotating the release cable, hoping that the blades on the release cable would eventually line up with the release mechanism (so that the release mechanism could slide between the blades, giving us a little more travel. (not sure if any of that made sense, but without diagrams that's my best explanation) Whether or not that actually occurred or not, I don't know since it was very hard to look at the mechanism and try to move it at the same time. After hours of exhausting work, we were able to get the travel we needed to pop the hood.
What a HUGE pain in the butt. If ANYBODY has any sort of modification idea or plans for a different way of releasing that hood mechanism other than that sideways pull thingy that Mercedes came up with, I'm all ears. I couldn't even imagine what would be necessary to get the hood open if the cable had snapped.
The cautionary tale here is DO NOT LOSE THAT PIN. I will be looking directly down into that hood latch mechanism every single time prior to closing my hood from now on and testing the hood release mechanism prior to closing the hood. I wouldn't wish this ordeal on anybody. I have included an image of the "tool" we used to get it open.
HUGE kudos to Lorenzo Morizio who worked tirelessly to get this done.