Sorry for your bad experience. Don't despair. Lot's of new owners have had thorough, lengthy walk-thru's and couldn't remember any of it! However, this guy was dead wrong, and I would complain to his boss.
Read and ask questions, here. Go to YouTube and look up videos. Camp Driveway is a good way to familiarize yourself with the equipment. If you do have a problem at a campground-ask! All of us were new, once. Campers are very helpful, plus the campground staff can help you. There will be other bumps in the road. Make sure to take a 'Plan B', duct tape, and a sense of humor. Have fun!