The oil it uses is actually synthetic 0w40, available at any dealership, and a whole lotta parts stores. The plugs are a non-issue as they last 100,000 miles.
Now, onto the truck. I used mine to tow a 12k 5th wheel and it did a great job. There was only twice when towing 12k in the Canadian Rockies that I had it to the floor and was unable to gain speed on a steep grade. It got 7-9 mpg (usually 8ish) when towing that weight. I was a very happy 6.4L owner. Losing the truck in the process of going through a divorce is the only reason I no longer have it.
I would buy another in a second if I needed another HD truck. Oh, and my trucks before it were both 5.9L Cummins diesels, and I towed the same 5er with that 07 megacab Cummins.