While at the Auto Parts store I would have had them do a load test on your battery. Advance Auto Parts and Auto Zone can do this.
Based on what you've stated, to me it sounds like a weak battery under load, or bad connection on battery to starter (check connections/clean the battery connection).
You've stated you have your dash lights, this indicates your ignition switch is ok. (My ignition switch went bad on my 1995 Silverado, however when I turn the key to run...nothing or no lights.)
Hope this gives you a little more insight.
Daniel
Wow...JUST WOW!!!! So sorry this has happened and hope it gets fixed! Must be a loose ground wire or loose connector somewhere. This is crazy, I'd be very upset too! Keep trying different dealerships.
Daniel
I'd first check my battery voltage after sitting all night. If good battery is probably fine. If it does it again, my guess would be a loose connection or a electronic issue. I don't think its a security issue because you still should have had your dome lights on. Hopefully it was just a fluke.
Daniel
I see people all the time do the following, while truck is still rolling backward, they place the vehicle in drive and vise versa. Thats not doing your clutch packs any favors, nor the rear-end. Vehicles are expensive, I believe in taking care of them.
I believe what your hearing is in the rear-end, the play between the rack and pinion gear. Also the gear selection from drive to reverse. Yes its normal. Over time it will wear more, best thing to do is come to a complete stop before changing drive to reverse (vise-versa), change the gear oil when recommended, and take care of it/etc.
Daniel
This is my 2010 GMC Sierra SLT "All Terrain" 5.3L (325ci), 6L80e tranny, 3.42/G80 rear-end, Airaid CAI, Flowmaster super44 mandrel bent single dual out exhaust, Magnaflow exhaust 4" tips, Diablo 93 octane tuned, AFM turned off. Hope y'all like