Calvin, you've selected the right range of years with the 6-speed transmissions. In 2012 GM put in the updated navigation system, 2010 on have USB charging ports. There are improvements to the Tow/Haul mode programming in those later years as well if that is important to you. 2012 the Hill Start Assist and Trailer Sway Control became standard and in 2013 Powertrain Grade Braking in Normal Mode was added.
If you live in hot climes, the K5L enhanced cooling package might be important to you, as well as 3.42 gears (GU6) and maybe even the Integrated Trailer Brake Controller (JL1) for more pep and convenience when towing.
If you don't care about fuel economy and a little more truck like ride, get a 2500. The suspension and running gear is twice as sturdy and there's no AFM. If you get a 1500, you can yourself or have someone physically remove the AFM system and get it tuned to make the engine near bullet proof. The last year for the 2500s was 2013. Look up Duraburb on youtube.
With your purchase, buy a Tech2, so you can quickly and accurately diagnose the truck throughout its service life with your family. The only caveat is that it's supposed to only work up until 2013 but I believe that these GMT900s kept the same computer system and interface in 2014, but not 100% on that. The MDI GDS2 software and a laptop is what replaced it for 2014-Current.
It's a shame that so many of the K2s are plagued with the problems you're experiencing. Please let us know when you find its replacement, both of them!
