you can use remository to upload files and let your user do the same, more informations on the link below.http://www.remository.com/rem/view/ReMOSitory/ReMOSitory-basics/What-is-ReMOSitory/
I'm not sure i get it, about the discussion form. Do you mean people can comment your news/articles ?
if this is the case you can add a comment system for all your news. Many comments components exist, have a look here => http://extensions.joomla.org/index.php?option=com_mtree&task=listcats&cat_id=1764&Itemid=35
Some are commercials and others free.