How do you change the oil on a fiesta diesel?

The old straight diesel engines had an oil filter which is quite different to the filter fitted to the modern Tdci, and the sump plug was a different size, but to answer the question, get all tools ready for when you get back off a journey with a hot engine because the oil will drain more easily when hot. Ensure you can park with the car level and with clearance to place an oil drain tray under the sump, or jack up the car front and rear to keep it level. Remove the sump plug whilst the engine is still hot and let the oil drain into your drain-tray (a deep cat-litter tray is good). Lift the bonnet (the term 'hood' is not proper English) and remove the oil filler cap, putting a piece of clean rag or kitchen roll over the filler hole to ensure no dirt gets in. Once the oil has drained, remove the oil filter and fit a new one. Clean the sump plug and screw it back in. Put some rag around the oil filler hole to guard against spillage, and pour in the correct grade of oil (the older straight diesel engines will probable require a different grade to the modern Tdci engines. All modern Ford petrol and diesel engines take 5w/30 grade) until the level reaches the top mark on the dip-stick.