This is going to be a bit of mess. Is there a particular reason you are switching these many variables at the same time? Personally, I would just redirect all url's from old to new domain and handle all the conversions at the new domain.
That being said, I'm not sure if you're aware that you can still use VBSEO format url without actally using VBSEO itself?
You should really plan this carefully before you make all of these changes.
For redirecting from old domain to new domain:
Code:
Options +FollowSymLinks
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} !^talknex\.com$ [NC]
RewriteRule ^(.*)$ http://www.emountnation.com [R=301,L]