Changed my spark plugs today and mostly all of my driver side had oil and thr first and third on my passenger side had a little bit of oil... Any one know why? Any help is appreciated

 

bad rings or bad valve seals probably. check your valve cover gasget.

 

I'd suggest a compression test. It could be valve seals or rings.

 

Thanks!

Now is this a serious problem? I mean the truck runs fine No CEL No rough idle

 

You need a compression check to verify if it is the piston rings. If it is valve seals, I know back in the 70's there was a fitting that screwed into the spark plug hole so you attached an air compressor to it. That kept the valves from dropping in the cylinders, who knows 40 years later what is now available. You also will have to compress the valve spring, and remove the retainer, and spring. Replace the seal, then then reinstall the spring retainer. Not that bad of a job, certainly alot better than piston rings, but you will need some tools.