The answer is yes - you have to crawl under the car, on jackstands with the right front wheel removed to get access to the plug. I am thinking about draining my '85 300D block because I am about to replace the radiator. I can see something like sealant paste under the plug. I have not tried to break it loose yet, but it may be very difficult, if not impossible, without heating it with a torch.
And no, you do not need to remove the turbo to get to the plug. It would be way too much work.
I tried removing the block drain plug on my '95 Nissan pickup and could not break the plug lose without risking breaking it. I do not want to do that. I wonder if this is going to be the same thing.