Congrat's on your purchase, sounds like a nice truck.

Although as it's been pointed out that the battery is not that big of a deal, i would be hesitant keep a spare battery in a sealed container - I'm not sure if the suggestion was for it to be sealed or not so ignore this if it was not. Some batteries do not need to vent, some do. Either way I would avoid having one in a sealed plastic container inside the passenger compartment.