Integrate & Fix Errors with Payment Sense Gateway for Magento

General information for the website: DIY Store Description of requirements/features: Need Payment Sense Integrated and Fix of Errors Had someone integrate the payment gateway but kept showing errors (like Fatal error: Call to a member function toOptionArray() on a non-object in /home/platin22/public_html/includes/src/Mage_Adminhtml_Block_System_Config_Form.php on line 463) Been told its conflicting with something else in magento hence why causing these errors. Extra notes: