Need to update a site from 1.5 to 3.1. We need everything to work as it does right now.
The template needs to remain the same.
Some pages are registered only
There is a custom database search (code is php, using directPHP plugin right now.)
There shouldn't be any 'custom' development, just need to migrate to newer system.
There can't be any downtime, this must be tested on dev server, need seamless transfer.