I haven't, but I've found a few products that I've looked at:
http://www.dronemobile.com/
and this one: http://www.viper.com/smartstart/
The drone mobile looks really cool, but the minimum fee is $50 each year. For GPS tracking, $120 per year. That's on par with onstar through GM however...
Wheel selections are really a personal opinion.
With your color, a black/machined combo or a chrome would look nice... or if you feel like spending some money something like this: http://www.fueloffroad.com/fuel-forged-b-4107.htm
or American Forces, they are nice.
Engine/Exhaust braking?
Check this thread: http://www.ecodieselram.com/forum/threads/factory-engine-braking-feature.482/
Welcome to the forum, we're glad to have you!
I haven't heard anymore recent reports, are all others being held as well still? I know GM still hasn't released the 2017 Duramax yet as well. Ford's '17 Powerstroke is out on the market already however.
Sorry to hear of the bad luck. Was the truck new when purchased? We've had a lot of member with oil cooler failures but it seemed like it was mostly 2014's.
Stick with the recommendations in the manual. Change your fuel filter more often than not.. use the correct oil as the TSB has changed it from the Euro Spec.
For performance, a tune is the best but you have a risk of loosing your warranty in event something catastrophic happen.