It's unlikely that you could permanently fix it yourself. Have you found the leak? As long as it isn't in the sidewall, they could patch it. I've had a couple screws/nails in my tires that they fixed and I never had an issue again.

While yes, you can plug one your self, discount will fix it for free as long as it’s not in the sidewall. I do as much of my own maintenance as I can but I take my leaky tires to discount lol