This is almost the same method as changing the spark plugs. So the first few steps I have taken from my Spark plug replacement Guide.
This is easier than you may think, as long as you take your time esp when it comes to taking and putting back on the manifold.
Firstly take off the engine cover by removing the 4 torx screws circled.
Next undo the torx screws on blue, the 7 manifold bolts in red, don't worry if the whole bolt comes off with these, some will, some will release just the nut, and release the jubilee clips in pink. Also the brake servo pipe will need to be undone, this is located on the back of the manifold next to the blue highlighted torx bolt that needs to be taken out.
This will allow you to take off the manifold and move to the side enough to work with, and you will be left with this. I would strongly recommend you put some tissue paper down the holes in the middle of the V as I have, if you drop anything down there, the spark plugs will be the least of your problems!!
Now its just a matter of taking out the old sparks and replacing them with your nice new ones.
If they come out like this, and covered in oil, then your rocker cover gasket has probably gone, and this will need doing as well.
To do this you need to get a set of the gaskets Vauxhall want about £50 quid to do both banks, but I was lucky enough to find some on eBay for about £20. (shirley9293 is the user ID if you want to look)
OK, firstly you'll need to take off the covers by undoing all the bolt highlighted in yellow
You may find that you have to undo the two pipes on the rear cover (highlighted in red) to get to the two bolts underneath.
When these are off, replace the old gaskets with the new ones in the covers and put the covers back on in their position.
Putting everything back on is the opposite of taking it off, but when replacing the manifold make sure all the pipework is where its supposed to be. And its a good idea to replace the manifold gasket at the same time.
There are also a couple of pipes that need to be reconnected, the easiest is the one highlighted in yellow in the above picture, and another that connects to the manifold next to the ICV on the block right side.
