Back to the OPs question following a good but typical sidetrack discussion.
He said he will be using the truck bed very little/lightly.
Not worth spending the $500+ to get it lined for that type of use. Certainly not right away. Nice shiny truck bed will likely still be a nice shiny truck bed years from now based on how he is going to use the truck.
Now many new tucks come sprayed from the factory or at the dealer level or its thrown in for "free". If that's the case, great, if not I'd save my money and decide if it's needed next year or 5 years from now.
Plus being in WI, the inside of the truck bed will be way done on the list of areas and parts that will rust out eventually.