regarding timing refer to the manual, in other respects remove as much stuff around the pump as you can to make working easier, it is when struggling to line up a difficult to get at injector pipe that dirt can be introduced, it will take a lot longer to remove and replace all these bits but is will be l a lot quicker than having to do the whole job again if you get something wrong because you could not get at it properly, and most important of all CLEANLINESS clean the whole area with engine cleaner and hose or better high pressure wash, as soon as you disconnect any fuel pipe, cover it, bits of plastic bag and rubber bands are good, or tips of rubber gloves as long as the diesel does not affect them, remember CLEANLINESS, the element of an injector is so finely engineered, that if you remove the pin and hold it in your hand and place the body on a metal vice for a few minutes then the pin will not go back in till the temperatures equalize, and the last very important tip, is CLEANLINESS, Rick