Easy job with only one "gotcha":
Clean IP (no dirt in the injetion system, please!). Remove injection lines on both ends and set asside (note that you will probably need new plastic clips, they all break when you unclip them, and the lines will fatigue if you don't have them clipped down....).
Not arrangement of the lock rings and remove. Screw will be very tight -- no antisieze at the factory, I think. Lift off rings.
Unscrew pressure valve holder (I recommend on at a time) and lift off. Watch for the spring, it tends to stay in the holder if you don't pull exactly straight up, then falls out and drops on to the dirty floor.
Copper seal is sitting on top, lift off with a pickand replace with new. Remove old o-ring from holder and install new.
Put spring back in place if it came out, then fit holder back in. Run down finger tight, then tighten to 25 ft/lbs TWICE without loosening, then again without loosening, to 30 ft/lbs. Failure to correctly torque is the only real problem here -- the seals will leak of you don't torque properly, and that will cause serious injector knock and loss of power caompanied by severe engine shake (affected cylinders don't fire at idle). Got my 300D cheap because fo this..... If you get these symptoms when you restart, loosen and retorque the pressure valve holders.
Refit lock rings and pre-load gently to hold pressure valve holder tight, then tighten screw. Please use some antiseize.
Refit injection lines to pump and injectors, but leave injector end loose by about 1/2 turn. Crank engine with your foot to the floor until all the air is purged out of the lines, then tighten cap nuts and crank til it starts.
Best to do this with the engine hot -- easier to start that way.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!