Twice, I have been quoted $800-1200 to rebuild an LD28 VE IP.
The LD28 VE is not like the majority of them. It may share some parts with the VW Six, but not many with the very common Four cylinder version. It's expensive to rebuild.
I have a used one, untested from a JY 1982 AT, that I would sell, as well as the brand-new one listed above.
In general, a VE IP can be resealed with only a very patient hand and a very few dollars of parts. It the leak was at the front shaft seal, you don't even have to remove the IP to replace the seal. If it's leaking back at the high pressure head ("distributor"), the IP has to come off but again it's fairly cheap to reseal it.
[edit 18Jan2012: someone has replaced that o-ring with the IP on the car, but it wasn't in a Maxima. See
this thread.]
I think that it's when the head or plunger or governor or feed pump have to be replaced (SVO, WVO, other alternative "fuels") that you have to have the major rebuild. Or maybe they all have to be rebuilt and I just don't know it. I have yet to hear from an LD28 owner whose car doesn't smoke heavily on hard acceleration (very much unlike the SD22).
Given clean fuel, the VE IP has proven to be durable in most areas. The shaft seal is an easy fix, now that
Matt has done the research.