OP, glad to hear you are happy with the outcome. And again I go back to one of my earlier posts in that it's good to see guys keeping an older, paid for truck on the road, and modding it if they feel the need, for current duty. There is a LOT to be said for a vehicle that we don't have to have a fortune tied up in, that can still do the job, and also make us really enjoy driving it. I feel the same about one of my trucks, a 11 year old vehicle that I love driving every day.
I'm still curious what exactly the gear oil is they installed in your diff. If you know the brand, weight and type, that would be interesting info to share with us.
As a side note, I ran royal purple ( syn ) for a while in the Nissan diff, and sent a sample of it after about 25K miles to blackstone lab. The report was essentially identical to the report I also did earlier with Nissan branded diff oil ( no idea who makes the Nissan oil ). Royal Purple sure is costly !
To those who keep their vehicles a long time, having fluids analyzed at a lab is a fun exercise if you are a vehicle information junkie. I use blackstone-lab. It's fairly costly though if you do it often.