1. That is possible. Do some searching here, you will find what you need.
I managed the moving of a good sized EZ-Board over to vB about two years ago. It had about 15,000 members and I think about 500,000 posts at the time. Since EZ will not give up database backups it is a bit of challenge. First, vBulletin staff will handle the majority of the migration for you. This is due to the fact that is uses a special script that "spiders" your EZBoard to collect all the posts and such. Users will have to register again at the new vBulletin. Users are not moved, PMs are not moved, etc. Now, for posts, existing posts are treated like a guest post but the usernames are correct. So there is a script available that allows you to merge all of a user's previous posts into their newly created vB account. The script has two fields and you enter their previous EZ username and their newly created vB username and it will merge all the old posts into the user. This is done one at a time so it is obviously used sparingly. We did it for all the staff and over the course of a month or so we did it for about 200 or 300 of the most active members that requested it. For the most part it was not a big deal though since the old threads still had their username there, it's just it was not "linked" to the new account unless they were run through that script.
I think it was Freddy that does the EZBoard imports and he was fantastic. Had the whole thing done in about two hours if I remember correctly. You do have to sacrifice a little bit with the move (not being able to import PM, users, etc.) but you need to think long term. With EZBoard, they own your content. There is no other forum software company that I know of that offers free (with a license purchase of course) migration and support. If you are going to do it, do it quickly. The longer you wait, theoretically the harder it will be to get away from EZ.
The board we moved was
www.LostTV-Forum.com and with yesterdays S4 show airing we are about to break 2 Million posts.

Overall a great success.