How can i fix my Citroen Xara Picasso 2ltr hdi trip computer?

I have a problem with my Citroen Xara Piccasso 2Ltr Hdi 2003. It all developed after i put Unleaded Petrol in my Diesel Car I Know I know!! didn't drive it tho but i had to drain it through the end that goes into the filter, but the engine went into economy mode and after 4 seconds stopped pumping so i had to switch the ignition on and off every 4 seconds. Then my mpg reading was displaying 141mpg at 70mph and now a warning light displays "Passenger side airbag fault" and the automatic door lock will not stay on. Any help/Advice would be much appreciated.