Few things to start with:
1. Have you tested your module on X2.5? if not this could be your bigger challange than Xoops core. there is a lot of change on PHP 5.3 and MYSQL side.
2. Is it an option for you to consider a fresh install with data migration(mey be applicable for static or simple sites)?
I am not a professional or a xoops exert, but will try my best to help you.
Good Luck
Deepak