It is your rear cam plug seals. They cost about $5 ea. Takes about an hour to replace them. You are lucky you made it to 165k before they started leaking. They are a common problem with these engines, but not too hard to fix. There are two little bolts that hold on the cap for the seal. The seal is an O-ring about an inch in diameter. Don't sell your truck because of this leak.

'90 Montero XLS (Sold, sadly)
'95 Montero LS 160k
'03 Montero Limited 30k