Which engine? If it's a Thor, you need to drain a few litres of coolant and remove the top inlet manifold... this entails a fair amount of work but it's straightforward ...RAVE is your friend. Also check PaulP38's website for pics. One tricky bit is disconnecting the fuel rail from the flexible fuel line...
Take a lot of photos and seal bits in clip lock plastic bags with labels inside the bag ...including a rough sketch as to how / where they fit...sometimes photos are not enough:angel:
It's going to be a long exercise if you're going to do a DIY comparison between different sets of injectors... but you'll certainly be an expert in dismantle/replace!
One more thing: there's a metal gasket required between the upper manifold and inlets on the Thor engine. Get a replacement and smear it both sides (clingwrap thickness only!) with Locktite 518 to ensure an airtight seal.
Good luck with it!

