The car definitely looks in good nick.
I've seen fully reconditioned engines available for less than $10K.
Here's one for $6300. But that may not be necessary.
If the fins inside the turbo are moving it might also not be the end of the world. HOW they're moving is an issue. If the shaft holding the impeller (the round thing with the fins) can be wobbled from side to side then yes the turbo will need replacing. You have a choice of 2nd hand from a wreck (maybe don't, because you don't know how it was treated), refurbished (may be ok), new Chinese (possibly just fine, I have one, had no trouble with it) or new genuine. Genuine will cost anywhere from $1500 or so (Brisbane turbo supplier) to about $4K if you get it from Nissan (and it is quite literally the same thing).
Oil passing through the turbo - it's supposed to! The oil vapour from the crankcase ventilation system (PCV) enters the air intake just a couple of centimetres in front of the turbo. That's what it was designed to do!
Here's what I'd do, mostly in order:
1) Check the turbo to see if that shaft really is wobbling or not. This is probably the worst thing to deal with $-wise.
2) Change the engine oil. Put a whole fresh lot of proper diesel engine oil in, add some extra cleaning shit from Nulon or Liqui Moly or whoever and run the motor until it's warm then dump all that oil and refill with fresh. Put a new filter in now too. See note at the end of this post.
3) Remove the EGR valve from the end of the intake manifold. Using a vacuum tool, suck the muck out of the intake manifold. This can be done at any time.
4) Block the EGR tube (take the gasket off the end of the gold pipe, cut a copy of this gasket but don't make the large central hole in the gasket, add gasket cement and install both, with the original gasket on the intake manifold side). This can be done at any time.
The DPF can be solved in a number of ways. First check that you have one! Assuming you do ...
A) Replace the DPF with a new one from Nissan. This is ridiculously expensive (about $4K).
B) Get a second-hand DPF from a wreck. Again, you don't know if it's going to be good - it's a risk. I wouldn't.
C) Get a "DPF Delete Pipe". It removes the need for the DPF, it was about $1100 last time I saw one. Not my first choice.
D) Write to auggie here on this forum and ask him for replacement DPF sensors. Not sure what he's charging for them these days, but I paid somewhere in the $500-600 region and they just work without any fuss. I did have my DPF modified with a large chisel to improve exhaust flow.
Important note:
Diesel engine oil looks and feels very similar ot engine oil for petrol motors, it is quite different in its properties. Diesel accumulates soot from the blow-by, and blackens very quickly after an oil change, and in order to keep the oil galleyways clear, diesel oil has detergents added to it.
It's entirely possible that if your oil has started clumping up, the previous owner may have been using ordinary engine oil and neglected to change it. We used to have someone on this forum some years back who had experience with a diesel Pajero that had seen over 100,000km without an oil change and the oil was simply black but functional. I'm not recommending increasing the time between services, but the point is that 100,000km of driving didn't clump that diesel up, so it's possible that it was the choice of oil - and changing to the right oil might resolve your problem.