2006 Dodge 3500, valves have not been adjusted and heard the other day they should be adjusted at 150K miles, I have 190K on it now. Should I take it in to be done or leave it alone. Not having any issues now that I am aware of. Thanks

I have 325,000 miles on my 12valve and the only time I've had the valve covers off is when I advanced the timing 4*
I did run through the valves at that time and they needed nothing. I also re-torqued the head just for the he11 of it...
Cummins have a massive roller cam and lifters that live well under 3000rpm with about 60-70lbs of spring pressure so their pretty trouble free.
BUT, it certain can't hurt to pop the covers off and check everything just so you don't feel guilty about neglecting these old work horses...

Yes adjust them...if you can adjust the valves on you race car, you can do those. It's easy except for #6...most people say they run better after a valve adjustment.

The Cummins will use a two position adjustment procedure. There's a removable cap on the front cover that exposes the fuel pump drive gear. One adjustment is with the timing mark straight up, lined up with the mark on the front cover. Second adjustment is with the mark 180* straight down, lines up with the mark on the cover at the bottom. Won't hurt to check them, and will likely need a tweak, but won't be much. They don't come out of adjustment easily or often. I've seen them run 200k+ and the valves still be at the factory adjustment.