I believe the towing package for your truck would include the tow/haul button on the end of the auto shift lever that digitaldelay mentioned.
Again, I'm no expert as ive never owned one that new but I believe without that Z82 code in the RPO list and no tow/haul button yours isnt equipped with the trailer package.
Did some looking around and heres a couple good links I found. From what I gather the Z85 package includes shocks, tow/haul mode and trailer wiring. So it looks like yours is equipped with a tow package. Looks like Z82 is the HD trailer package.