I would not consider $53k for a heavy duty diesel truck a bad price but it is far from being a good price. If I were shopping for this truck I would take the time to work a deal and get the truck for $47k or less. If it takes me a month and dozens of hours to save $6,000 then I will do so and have often done so in the past.
My 2011 heavy duty GM diesel truck cost me $41,700 and including every available option except the nav system. In addition to the accessory and tow packages I got the dealer to throw in a bed liner, chrome side steps, and a GM diamond plate aluminum tool box. I bought the 2011 in October when the 2012 trucks were starting to arrive which helped.
You have more room to negotiate by selling your current truck later to a private party and not making it part of the deal and my going into the dealer the last weekend of the month and by talking to the sales manager or the fleet manager and not a salesperson whose $1500 commission is otherwise part of the deal.