did he give you a print out for your emmission or did he just do a visual on it and advise. if its a visual ul need to do the injector leak as it will alter your emissions to the point of mot refusal. a quick (altough not correct) costing of what youl need to put things right I.E oil leaks and turbo if needed then ur best option may be http://www.ebay.co.uk/itm/citroen-xsara-picasso-1-6-diesel-hdi-2006-complete-diesel-engine-/271739860349?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item3f44f5357d job done