James over on Grognardia talks about the list of upcoming Greyhawk products that can be found in Dragon #55.
Later in the post he focuses on this tidbit
As with most extensive dungeon complexes, much is developed and kept in the head due to actual play, and some areas are so difficult as to be impossible for those not used to our DM style.
A while ago I talked about Minimal Dungeons inspired by my reading up books on the early days of the hobby and this picture of Gary Gygax refereeing where we see part of his notebook.
As food for thought, perhaps a megadungeon "fit for sale" shouldn't be focus on presenting a product formatted like a tournament style dungeon. A dungeon map with every room keyed and written with a description. Rather a megadungeon should be focused on teaching the reader how the author ran the megadungeon. Accompanied by any aides the author used whether it is a complete map, geomorphs, or a sketch.
Keep in mind that the work for a dungeon (or even one of my Blackmarsh style sandbox settings) grows by the square of the area covered. A map twice the size is not twice the work but rather four time the works if one try to format it like a tournament style dungeon.
When it comes to the Greyhawk Dungeon, we do know that Gygax was able to teach how to run it at least once with Rob Kuntz. My opinion that any thing we can do as humans can be taught or at least explained to other humans.
Personally I was able to do a lot with the map to Tegel Manor because of the numerous notes and the room labels. The key served as a reference to specific content like monsters, and treasure. Occasionally a room would have a paragraph if it was a special encounter. What Tegel was missing was commentary and notes by Bob Bledsaw on how he ran the adventure. Plus a page or two page introduction for novices to running a megadungeon or for less experienced referees would be a good thing to have.