Good truck for 4000pds but without the tow hitch I agree it most likely does not have tow package.
I would second the Eco Diesel if you were buying new but highly doubt you will find one used to similar in price.
I have a 2011 and towed 8000 pads which was a little much for it. Freind has a 2015 with 6 speed and 5500pd trailer, tows like a dream, also used my 2011 and towed like a dream.
Have a second freind with a 2015 and the 8speed, tows about the same, no diff in MPG towing but not towing it is noticble better on fuel. Same tank size and the 8speed is getting about 750kms per tank while the 6 speed is getting 600km per tank. I have never looked into it if this may be pure luck or consistent with other owners.