New to this and need some input

[bowtoyclc]

It?s through a local dealer and as of yet there are no maintenance records or even owners manuals with the truck. I haven't run a carfax because normally they are a joke. In my state all it will show is the date and number of owners and if it has a salvage title. Any accident info by law must be reported by the owner and no one actually gets on carfax to report that their own vehicle was wrecked.
The truck started as instantaneous as possible and runs and drives fine. There seems to be no blow by, and that?s the extent of my knowledge when it comes to diesels. The underside shows wear and tear but nothing that I saw would lead me to believe that it was offroaded and abused in that way.
It has no winch, but does have the ctis.
Primarily this truck caught my eye because it?s local and for the year is the only thing I have seen in my price range.
I tried to check out all the controls and see if things worked properly but without the manuals myself and the dealer didn't know how to operate everything. (Such as defrosters, CTIS, etc)

One of my friends recognized the truck and said ever time he saw it, it had a 20 ft. trailer behind it, so I am assuming that it has done a hefty amount of towing in its life.