For those also about buddypress, In the plugins directory I found a tool called Ning network import tool:

https://github.com/boonebgorges/Import-from-Ning

You can upload your whole ning network into a buddypress installation. If you would like to test drive this to see if this works, I could trial you on a subdomain for little or no income so you could learn the basics of buddypress. Just a offer.