With your travel time, I would go to the show. Yea you might see pickles but mostly its old stuff. Half of the show of so is old military, the other half is other older guns and such. Its a 4 plus hour drive for me and I try to get down there a few times a year. Rarely buy anything but often see a number of things nice to look at.
If you have GPS navagation in your car, its pretty easy to get to. Paper map, a little harder but not impossible. 
As a bit of an added bonus, take a cooler as across the street is a Farmers market. Well worth the time to walk through. I keep forgetting my cooler but have seen a lot of very nice produce in there. 
Sam