I am under a Ford ESP extended warranty so I have all my maintenance completed at Ford dealerships. I keep track and go by a modified "severe usage" maintenance schedule, I don't wait for the truck's computer to tell me to change the oil or fuel filter.
However, all this depends on how many miles you tow with your truck and possibly even what type of weights you are towing.
IMHO it is more expensive to not only purchase a diesel, but also to properly maintain it. If I didn't have to have one for towing I would stick with gas.