try a new oil cap for the valve cover and an updated breather tube and that will help with your leaks.... as for the oil return under the turbo - you just have to replace that to make it stop making a mess
for more engine detailing stuff - this might help as well (I wrote this article for the nissan guys)
http://www.se-r.net/car_info/clean/detail_engine.html
here are some more diesel engine pics:
(Pics) More detailed engine bay by popular request...
(Pics) Doesn't this look so much better?!?!