This script should take any trixbox 2.8 system to the latest Stable FreePBX Distro of 1.816.210.58-1.
When done your PBX should be converted to an official FreePBX Distro system and allow you to upgrade in the future to all FreePBX Distro versions.
http://upgrades.freepbxdistro.org/trixbox/scripts/trixbox2.8-freepbx1.816.210.57-1.sh
As with all upgrades things can go wrong and there is very little error checking in this script as it just fast and dirty to get you moved over to a supported system. Let me know if you run into any issues and I will try and help address them.