So got to changing the PTU oil finally.
First I want to mention that I read this post well and got the recommended 3/8” socket wrench and an electric oil pump (great instructions in this post!), and they made things relatively easy.
So I was able to suck out ~300 of fluid. Was able to put back in ~ 500ml, so I believe I got most of it.
The fluid was not bad smelling, and flowed pretty well. I did not encounter thick/pasty sludge. So could be this has been changed before, or the type of driving the vehicle underwent was mild for these 138xxx miles? I’m leaning towards having been changed sometime in the past.
Regardless, it seems like it was a bit low since only 300ml or so came out. And I at least feel better about the vehicle since it wasn’t too bad, and it now has a full case of fresh synthetic gear oil.