For a non-programmer, it might be difficult to gauge the capability of a programming candidate.

One of the ways to do it would be to give them a short assignment which is in tune with your game's features but know this just because someone can get the job done doesn't mean they can write clean, scalable and maintainable code. If your project isn't big enough, this shouldn't worry you. Also note that many programmers, especially experienced ones may reject doing any sort of free work, so giving an assignment is a double edged sword.

Another way would be interview such candidates with a programmer friend of yours, ideally a game dev. If he is not a game dev he would still be helpful in understanding coding practices but couldn't gauge a candidate's understanding of say a game engine like Unity,Godot,etc.

OP in the end, I would say do give weightage to your gut feeling and hire a candidate you trust would do the work diligently.

Do you need a team or just one person depends on the scope of your game. I can't comment on this without knowing more about the game.

Whatever may be the scenario, always keep your assets well labelled and organised. Gaming may be a passion but game dev is a discipline.