I would like to pay off my home mortgage in one lump sum payment, so will I have to
Pay more than I currently owe or less?

You should contact your mortgage co

The payoff is going to be the outstanding balance, plus any interest that has accrued since your last payment. The payoff will also probably include a few fees such as the cost of recording the cancellation and a payoff statement fee, but those aren't usually more than $25-$50. So the payoff amount will probably be more than your current outstanding balance but not much more.