Upgrading from 1.12.15 to the latestest elgg release

Hi sir,

I was on long hibernation (:)). Now going to be a part of this active community again.

During my hybernation lots of water has flown under the bridge which I could not count. Elgg has grown like anything, the most powerful social networking framework.

And coming to the point my site still in elgg 1.12.12 version. I would like to update it and for that please help me by clearing my doubts.

1. What should be the updating tree for updating from 1.12 to latest 3.0 version ? Like first you need to update to 2.xx then to 3.xx like that

2. I found that the directory structure has changed.. what should I do to do a smooth upgrade with out loosing anything..

thank you for your help.