Dealer is probably right.
My '03 was in the shop for another issue. Tech ran a computer check on my injectors with his laptop. 2 were marginal so he replaced all 8 under warranty. When I saw the paper work, it noted that the customer complaint was fuel in oil.
I believe there is a 200,000 mile warranty on the injectors. Might be a real good idea to sit down and have a talk with your dealer. Didn't cost me anything to have mine done. 182,000 miles on the odometer. Can't really tell if it runs any better but glad to have the new and improved injectors.
Help out the technician who is going to do the work. Take it in the night before and let them have a cool engine to work on. If I were in his shoes, I'd greatly appreciate that.
Check the coolant level often for the first few days until all the air burps out of the cooling system.
Technician seems to think that folks who use their truck hard, pull loads and work them have far fewer problems with injectors than the folks who baby their DuraMax.
By the way.......... A DuraMax won't run on antifreeze. Had someone add a couple of gallons of green to my fuel tank. Was running up the road and the water in fuel light came on about 15 seconds before the engine stopped. Drained it out, replaced the fuel filters (yes got a fuel water seperator ahead of the factory filter) Didn't seem to cause any harm/damage to the injectors. Ran rough for a few minutes but rather than tow it, drove it home and changed filters again. This was at around 90,000 miles.