Oh…..
Every time I have bought a gas appliance from a big box store, they charged for delivery and installation, and then upon delivery the tech always had a flimsy excuse as to why they wouldn’t install. Every time. And I’ve heard the same stories from others. So I don’t buy from big box stores anymore.
To be safe and sure, though, just call your gas company. If your gas line is indeed safe, their tech will not be in any mood to waste time replacing a gas line unnecessarily. Yes it will be some money you didn’t intend to spend but aren’t your life, home and belongings worth it? Or, perhaps they won’t even charge if you just ask for a check of your line and shut off valve. You won’t have to wait for that! LOL. If they only do a check, you can dope the threads and tighten the connection in a few minutes, done. Most likely, though, the gas co won’t leave without doing the hook up and checking it.