I have checked for pending codes and found none then chalked the tires and found that they are not slipping. I was disappointed there as I am going to need new tires soon anyway.
The truck only has 55,000 miles on it but nearly half of that has been trailer towing so the plugs may well be nearing their end of life and the boots have seen a lot heat. I am going to follow the recommendations of new plugs and boots.
I am also going to check the transmission fluid. Even if it looks good I plan to change the filter and what is in the pan.