The cost of the 5tth wheel trailer hitch for your truck depends on the brand of hitch you buy and 5th wheel trailer hitches cost from $100.00 to $500.00
Then if you have a trailer shop install the 5th wheel hitch it will cost from $800.00 to as high as $1,600.00 for the 5th wheel trailer hitch plus the installation of the trailer hitch.
5th wheel trailer hitches are not all that complicated to install but if you want to make sure you get the 5th wheel hitch installed correctly so it's safe then it can be worth the cost of having a professional install the 5th wheel trailer hitch.
I've also seen some shops do the install of the 5th wheel trailer hitch for either $100.00 with purchase of the trailer hitch from them or even for free.