Joomla Ace Sef reconfigure, fix 404Errors

Hi, We have a portal with about 2000 articles running on Joomla 1.5.25, recently we installed the ACE Sef component and configured it badly, then we reinstalled it and changed some stuff in the configuration and now we have over 2000 Google Crawler 404 errors, and everything is a mess, we have more different urls for the same content, and we are lost, it's a chaos, page rank and visits are going rapidly down. We need an Joomla Ace Sef expert, Joomla master. Tasks: 1. Analyze our problems to detail 2. Suggest solutions into detail 3. Make all the agreed changes and/or modifications Issues: 1. To many duplicate url-s 2. To many 404 Errors 3. Google web master tools says over 1900 404 Errors 4. We lost 40% of our visitors