I just bought a used 2009 Ranger that has done about 275000kms. The engine is a 3.0 litre, 4 cylinder turbo diesel labelled as a "Duratorque". It has a chuffing noise when cold that goes away when hot. I took off the plastic cover on the engine and saw that one injector was leaking where it mounts to the cylinder head, obviously a seal on the injector. I'm new to these engines, what should I watch out for when removing the injector to replace the seal? Am I going to find anything unusual when I take it apart? TIA.