LOL @ being paid. I havent heard nothing about that. In your situation, it just validates my example above. Here the module worked on their test site, but not yours. Since you stated that you installed the module on a 'clean' install of Dolphin, there shouldn't be any type of conflict with other modules. You indicated that his change was to your core files which messed up your site. You would need to explain what file he/she changed (need proof positive), how it affected your site, etc. It would see more also need to be examined to see if the install 'required' modification to core files in order to work.

All in all, we (Moderators) will have a big task on our hands trying to get these disputes resolved.