ttrostel, first, I am not Intel, though I liked your disclaimer angles. They removed the document for a reason while they are reviewing it for an update. But I could say that it is hard to follow procedures for an image and source that is no longer available. Perhaps reposing your question to DiegoV_Intel who provided the correct answer might give you better clarification. As DiegoV_Intel is now aware, perhaps he can either post the older version or update us to when the NAG might become available. I wouldn't want for confusion to arise from a conflicting version.
If you look at your Edison console over serial or ssh, writing an application in c/c++ is available and the whole gcc command line compiler is available. Eclipse is available as an IDE via the iotdk.intel.com/ website