It's not difficult but it is nice to have something to refer to, especially the first time. Basically, the instructions save you time by guiding you (me) through what needs to be removed and what can be left alone. For example, the instructions specify which retaining clamps on the fuel lines must be removed. I know, anyone could figure this out but it is really nice to have a picture that points it out for you (that alone is worth getting a copy in my opinion).
On the 24 valves, you have to remove the intake plenum, high pressure lines, pull the valve cover, remove the retainers holding the injectors down, PULL THE TUBES (not all the way), pull the injectors, install new injectors, etc... .
The instructions will save you a lot of time and will give you some nice tips.