How do you change timing chain on a 1998 Nissan primera?

I am currently changing the timing chain on my 1998 2.0l primera. I have never worked on engines before. I started by buying the 'Nissan Primera 1990 to 1999' Haynes Manual - This tells you how to do it. You have to take apart a lot of the engine. One thing it doesn't tell you is that if you remove the cylinder head (to replace the head gasket at the same time), you don't need to remove the upper sump, but with this upper sump in place the timing chain cover will only lift away if you push out the oil pump drive spacer from the inside, reaching from below where the sump has been removed.