Make sure the recall work has been done, especially the water pump. The original pump in mine failed at 30k-ish miles and left us in a pretty good bind. Beyond that just fuel and do the recommended fluid changes. I've always run synthetic oil in mine mostly because of cold winters. If I didn't see below zero temps every winter I may just run the standard stuff.
I throw my exhaust brake on for more than just towing but I don't use it all the time. When I'm towing I always have it on and set it to Auto mode, along with T/H.
You won't regret stepping up to a diesel, and you got a pretty good one. I've really enjoyed my '15.
