I took the survey, and just wondering, what exactly is this "Darkshines", and how big will it be??
I'd ask/offer to be involved, but I don't even have a gaming PC yet ( getting one in about 5 months ) and I don't know Jack about mods or anything of the sort.
Anyways, good luck!
If you want to just follow the project and decide at a later time if you have something to contribute, that is fine. A website with forums is in the works (very near completion) and will have both user sign ups as well as a contributor application form. I already have a list of people interested in the project who have asked to be informed through PM's on the 3 communities the survey was posted, and I could add you as well if you want
EDIT: Forgot your other question. The size in terms of disk space will rely on the volume of voice acting and other media used. The http://www.thenexusforums.com/index.php?/topic/313854-darkshines-will-finally-come-out-with-skyrim/ was only 150 megabytes, but was half finished. If BINK videos is the way cutscenes are handled in Skyrim, I would expect a good 300 megabytes for just this type of content. (if we choose to do these)
As for length, that is largely up to the result of the survey and the direction we take, but we wouldn't call it an "Unofficial Expansion" if it was just a 5 hour side quest.
As for what the story exactly is like, you're going to have to wait unfortunately - as we want to make sure everything meshes with the existing lore beautifully
(and I'm still deciding what to keep/change/toss out from the old mod)