Advice for newbie

[Thinman]

* ok, I answered half my question, Cummins says Good day.
I’m a new member. No need for a life story, suffice to say I have a little mechanical background. My experience is mainly with cars, hot rods, and Harleys
I am looking at an 07 KW T 600. CM 870. Looked at it today. Two owners. A Midwest regional transfer company and a grain farmer. Odometer shows 700161 miles. The farmer said he has had the truck since July of 2012. Says he he puts on around 10 k a year, spring and fall.
The engine had been running for about a half an hour before we arrived. Engine is covered in grain and gravel road dust. No apparent oil leaks visible, no oil on ground under truck no evidence of coolant leaks. The oil pressure shows a steady 30 lbs and jumped to 40 with a nudge of throttle. Went right back to 30. The thing that gives me pause is what I believe to be the egr valve is unplugged. Removed oil fill cap and didn’t observe any blow by. Is 30 lbs about right or low? I am far from knowledgeable, but everything I looked at appeared to be original. Farmer said other than oil changes and basic pm, he hadn’t replaced anything. I called Cummins and the guy said the VIN shows nothing. I called MHC Kenworth and the only record they have showed a hose (?) problem in July of 2011. The basic truck seems solid. Is 30 lbs normal or too low? something else that gives me pause is what I believe to be the egr valve is unplugged. Mechanically seems to be a solid truck. Is the oil pressure and unplugged egr valve a major concern?
Ok.... I found the answer to oil pressure. Cummins says a minimum of 15 lbs. so I’m good there. Now the unplugged egr.