As stated earlier in the post, I'm no mechanic but I will show you how I removed my 4th Injector.
Ok, this is my engine with the black plastic cover removed.
1) Allen Key - remove bolts fastening down the Injector wiring loom. (not necessary but generates space for Injector to slide out)
2) Unclip Electric plugs. (Again, I unclipped the larger plug as well as Injector 4 Plug to gain more room)
3) 8mm Socket - remove Rocker Cover, 7 bolts in total.
4) Pliers - remove metal clip fastening fuel nipple.
5) Fingers - remove fuel nipple.
At this point, the Rocker Cover will be out of the way and the wiring loom will be loose and able to be "gently" pushed to one side.
6) 14mm spanner - unfasten nut on metal fuel pipe.
7) Allen/torx Key - remove the last two bolts.
Now your Injector will be loose and should slide out, if not, gently prise it out in an upward direction - there's nothing else holding it in.
Ok, now you should be able to remove the Injector with your fingers.
This is what it looks like.
With a torch, locate the old Injector Seal which will be at the bottom of the Injector Chamber. I used a torch and made a little hook out of wire to pull in out. (Seal A in the picture below).
With a soft dry cloth, give the Injector and Chamber a good clean out.
In the Picture below are the Injector Seals/Washer I purchased from my local Citroen Dealer.
8) Seal A can be lowered into the chamber, don't panic if you drop it into the chamber, just make sure it is flat before the Injector returns home.
9) Replace Plastic Washer B if the old one is damaged, this is located 2/3 up on the Injector.
10) I slid the Rubber Seal C onto my Injector rather than fastening it in
place on top of the chamber because it was much easier lining up the Injector when it went back in.
This is where your Seals and Washer go on the Injector!
Ok now reverse steps 1 - 7 to replace.
Take caution not to over tighten the two bolts (7) which fasten the Injector in place, I'm told they should be tightened to 5 nm. Plus make sure you tighten the bolts evenly, especially if you have slid the Rubber Seal C onto the Injector.
The biggest problem I encountered was re locating the Rocker Cover without kinking the rubber gasket. This took me a couple of goes to get it right.
Good luck and I hope this is of some use...
Stu, forgot to answer your questions mate.
Yeah I removed and replaced the Seal's because I could feel air discharging from Injector 4 (only) on idle. Seal A was worn out, Seal C had split and there was nothing wrong with the Plastic Washer B, but replaced it anyway.
Before I replaced the Seal's, my van's idle was rough for a minute or two on the first ignition and coughed out small amounts of blue smoke from the exhaust, this stopped when the new Seal's were fitted.
No I didn't re-pressurise my fuel rail, not sure if I should have done but didn't experience any issues in not doing so!
The main tell tale sign for me was the sound of short bursts of air discharging.