If your modification considerations are improved longevity, fuel mileage and daily driving and towing performance, you may wish to consider the following.
The below is a common sequential approach to mild mods:
1. Disable EGR, reroute PCV.
2. Install 4" exhaust; cat-back is good, front pipe and cat back is better!
3. Install cold air intake; stock paper element filters best.
These mods alone are relatively easy, inexpensive and will provide improvements you can feel. To obtain even better fuel mileage and daily driving and towing performance:
4. Install Boost Stick
5. Install mild tuner; (Edge EZ is an excellent choice!)
If you tow heavy, you may wish to consider installation of gauges. Even a stock LLY can experience excessive EGTs under certain conditions!
The above mods are very mild; relative to what's available, and are easily returned to OEM if necessary.
I'm no expert and have undoubtably omitted several good ideas, but this will get you started!