Not that I know of. The main guru of it is Lady Nerevar. You can ask her I suppose although I'm sure she gets 100 billion messages a day. lol She's the leader over at Tamrielrebuilt.org
^ Someone is completely wrong ^. Lady Nerevar isn't even an administrator at TR anymore, and for the last two or three years, she's been Oblivion-only. She hasn't ever really been involved with quests that much.
We don't have a "main quest", just long and well-developed guild/house quests. As for a walkthrough... see the above post by Mantriel.
As for your newer question, we've released two parts, and plan on releasing at least 6 more. Remember, we're making all of the mainland of Morrowind. So far we've just released the eastern bit.