Reengineer Expression Engine web Application

I have a web portal that was developed using Expression Engine and provided to my client a few years ago.

The client has upgraded their server environment and the portal no longer functions correctly.

The original developer is no longer available to work on a fix.

I need somebody to look at the original application and the upgraded server environment and produce a revised version that has the same functionality but is compatible with the upgraded server configuration.

This is an urgent requirement