Kudos to his ingenuity

Sounds like he's done some of the leg work with the stove.
He'll need a T adapter connected to main gas line, or at least a way to tap into a gas source, with a gas shutoff valve directly after.
Gas rated thread paste, and a spray bottle of soapy water to spray over all connections to look for bubbles (air leaks)
I'd probably recommend 3/8" copper tubing with compression fittings. Paste isn't needed for these.
Then he'd just replace the electric burner with a gas one, and run the gas line where he ran the wire to electric element.
Ya'd also need a regulator to control gas flow, and maybe an electric button igniter if you wish, like they use on grills.
That all said, I'm scared of any gas work, and it's the one thing I'll always outsource! But it can be done and people do it.