Switching from Invision Power Board 3.3.4 to vB

[cigarman2k]

I am planning on switching from IPB to vB. I am suffering in SEO ever since the version change in 2010.

Here is what I have:
IPB 3.3.4
1.2 million posts
12 year old forum
Large photo gallery

Can my site be converted to vB? I don't want to lose any of my posts/threads, and also I want to preserve the photo gallery.

Also, will my URL's change? If so, how does that affect SEO?