Virtuemart Joomla debug/fix fatal error on upgrade

I have a Joomla website with Virtuemart installed. The current versions are: Joomla: 3.4.8 Virtuemart: 3.0.12 There were some core code alterations made to the site by a developer in the last few months and when we try to update virtuemart from a copy on our dev site to the latest version we get a fatal error - Fatal error: Cannot redeclare class vmVersion…… We did not get any errors when updating the software prior to the latest core code changes. The developer that made these changes is no longer available and cannot be contacted and he did not detail all the files that he altered. Some of the files that he listed were: \plugins\system\vponepagecheckout\assets\js\[login to view URL] \templates\cutegecko_us\layouts\suboo_custom\html\com_virtuemart\productdetails\[login to view URL] \templates/cutegecko_us/layouts/suboo_custom/blocks/[login to view URL] \plugins/system/vponepagecheckout/cart/tmpl/[login to view URL] \components\com_virtuemart\sublayouts\[login to view URL] \plugins\system\vpframework\helpers\[login to view URL] I have installed a copy of the current site on a development server and need someone to debug the problem that is causing the fatal error after updating Virtuemart to the latest version and get the site running so that both front and backends of the site are working correctly. This would include updating Joomla as well. I will need you then to detail what was done so that I can reproduce and update the live site. I have no time for automated responses I need someone with Virtuemart/Joomla skills so please respond with "debug" in your response to be considered. I need this task done ASAP. Thank you Steve