Some of your questions were answered in the comments you ignored, but here's a summary:
Where do you get it?
http://nwvault.ign.com/View.php?view=Other.Detail&id=1513with additional fixes that didn't make it into the patch...
http://social.bioware.com/project/3045/&v=discussions#filesHow can it be installed?
THE PATCH ITSELF: Unzip the download inside your Neverwinter Nights folder I believe. The instructions are in the readme document included in the zipped file.
THE ADDITIONAL FIXES: Place the files in your override folder I believe, although I think I may have put the erf file in the erf folder.
Does it cause stability issues? Will it cause stability issues with windows 7? Are there bugs that it creates?
I am using it and haven't had any problems thus far.
NOTE: You don't need to install the Community Patch for it to change the server's gameplay. What is necessary for that to happen is the server must install the patch. Whether you do or not won't affect your experience of Prisoners of the Mist. What it will affect -- if you install it -- are your single-player games.
