vb forum and blogs
 

I am currently running vb forum 3.8
I need blog for it, and I need it now.
additionally: I plan to upgrade to vb4 sometimes later this year or early next year (will see how it runs).

What whould proper sequence for me? Where can I buy (or it is free) vb blogs for 3.8?
How do I upgrade it later to 4.0?