remove the cover off the top which has 6 retaining bolts beneeth you will find the ignition pack it is a wide black object which has 3 bolts holding it in position so unbolt that carefully lift out the ignition pack store it safely look down the 4 holes where the ignition pack was and down there you will find the spark plugs - the gap should be written down in your manufacturers handbook sorry cant give any more info on the gap you could always phone your local citroen dealership for correct gap
james wood, June 2008