Congratulations on the truck! May delay any expensive trips, but hey there are many other campgrounds that wont cost you so much.
DEF is not bad, just keep a jug on hand just in case you forget to top it off. You will use more DEF under load due to the amount of fuel burnt it will need to regenerate more often. Running the DEF tow trucks and averaging about 9mpg in them we usually see about 1 gallon of DEF to ever 60-70 gallons of diesel. Plus with the DEF level gauge you will be fine. I bet you will find out that towing the trailer will be no different, the biggest thing you will have to get used to is the extra width of the DRW truck.
My next truck will be a DRW but that's after I have a solid commuter car as I just don't want to have to park at the commuter lot with the extra wide truck.