Firstly the washer can be replaced WITHOUT taking off the turbo, by using a 12 point flat ring spanner, as there is enough space to get enough "swing" at the front and rear, ie facing the turbo from the offside put the spanner level so it is horizontal, it's a squeeze but do able and bloody fiddly.
The turbo is easy to get off by undoing drain, oil feed pipes etc and then the four nuts using a spanner, or alternatively just unbolt the trousers and remove that way, as the trousers bolts/nuts are much more accessible.
Once you have the banjo off, weld a tall nut to the banjo, so it sticks out further, I did this to both of mine and it is kids stuff to remove them now if needed.
tabetha