There are some detailed instructions on the BMW sites as you have the bmw M62TUB44 engine, YouTube has some good videos on the timing chain and vanos procedures that will get you some of the way depending on how confident you are at spannering. It is quite involved and as said already you will need some readily available special tools.Does any body have any video or detailed instruction on how to change the head gaskets?
The oil leak in that corner if it’s the one next to cylinder 4 is normally cam cover or the degraded pcv pipes and oil return pipes.That corner on the block is where I kept having an oil leak I couldn't find. It just kept smoking in that area. Can you explain the small non return valve issue?