Having replaced them on my car, the difference is tremendous, from an embarassingly long time cranking to starting almost immediately. DOn't worry about inspecting them, just change them if you haven't already done so. My car as a 2001 model low mileage and mine were shot.
Remove the central engine cover, the one that runs front to rear across the top of the motor, by taking out the three allen screws. Slide the cover out forward towards you. You can the clearly see the injectors and will notice that they have rubber pipes, covered in a woven fabric, linking one injector to the next each in turn with the front most one going back down to the injection pump. These are a push fit but will have gone hard, a pair of long nose pliers will be usefull to pull the pipes off ( and to retrieve the bit of pipe left behind as they will all break when removed) Mine had been weeping a small amount of diesel as the fabric covering was oily on some of them. To replace them simply push on the new ones untill the pipe is all the way down to the bottom against the injector body. Now be prepared to be amazed how easily the car will start!!
I'm not sure if the problem is air getting into the system or if it is simply allowing the diesel to syphon back from the pump, but it really made a huge difference to my car.
Unless your car starts almost instantly with no cranking (click,broom) then change your pipes.
My car is just six years old and these pipes were in a terrible state, they had gone hard and they were splitting so I plan to replace mine now every couple of years at a coinciding main service.
I hope this helps.
