Use Google Maps for routing.
Gasbuddy for cheaper gas.
Campendium and then follow to the campground link to verify. (I often backcheck via other sources once I pick a campground)
Keep in mind with credit card charges, they put the money back in your account while they sort things out. The merchant can submit back that it's a legitimate charge...then you have to submit back...this back and forth can go on for a while depending on if one side gives up. Given how long between the purchase and the challenge, you might lose simply based on waiting too long. Your best hope is it may not be worth the merchants time to challenge it.