gday mate, I went through the same thing last year (mine was a turbo bearing failure) This is how i went about fixing it:
Option 1:
Sent it of to Nissan, quoted about $15000-$20000 for a new engine installed with new turbo and recon injection pump. Needless to say didn't go down this path!
Option 2:
Second hand motor, you can get one for about $4000 - $5000, I personally wouldn't go down this path if you are wanting to keep the car.
Option 3:
Pulled the engine out myself, sent it off to Central Diesel for a complete rebuild. I supplied the parts which I got from Engine Australia, this was about $6000. New turbo, injectors and rebuilt fuel pump about $4000 all up. So grand total about $10000. If you do this they key to success is to label everything carefully and be organised, those zip lock bags come in very handy. If you send it off to a rebuilder make sure you list everything you give them and have them sign off on a parts list, as they will lose all sorts of stuff, my flywheel went missing, got it back though. When selecting a rebuilder, go check out their workshop, if it is a mess, stay well away.
If I did it again, I would buy a new crate motor from Nizzbits, I reckon that was about $8000 but does not include turbo or fuel injection system, at least this way you get the newest engine available
Not sure if you are looking at doing the work yourself, if you can you can save around $5000 in labour but it is a long and difficult process, a good learning curve though and pretty enjoyable when you turn it over for the first time!
If you have any questions, please let me know.
Good luck.