This forum is littered with people that haven't had any luck getting info or help from Nissan head office, but I'm sure there is also people who have had help. Like all companies Nissan are in it for the money and will prove as hard as they can that they aren't at fault. it sucks but it's the way of the world.
There is also a thread on here somewhere (search is you friend) about removing the DPF if you want to go down that path.
Two choices in my view buy a second hand one from a wrecker for $1k. Or as Krafty recommends remove it completely which is what I would do. Actually past tense - have done.
Don't bother with Nissan as the DPF is part of the exhaust and therefore viewed as a consumable.