1. That is already included in Nuke. GO to Admin/Messages. The message box will appear at the top of your main page. It's the same box you see when you first setup Nuke. The one that Say Create an Admin Account now.
2. There are addon blocks for weblinks on other sites that are much better than the standard one. Try
http://www.nukeresources.com for starters.
3. Have no idea
mikem