I am looking at moving my website and forums over to a new server, Was thinking this may be the best time to bite the bullet and upgrade to 4.0.x

How would I do that?

My suggestion would be to migrate your community/website to the new server on your current 3.4.7 version, make sure everything is working as it should, then upgrade to 4.0 by following these instructions: http://community.invisionpower.com/4docs/getting-started/install-and-upgrade-r8/