Definitely go with a pellet stove to supplement the oil. Don’t replace the oil burner if it runs fine. At 5 dollars a bag it is cheaper to run than oil at 2.50 a gallon. Buy it by the pallet and it is even cheaper. No special venting needs other than the small pipe. Always nice to see a flame if you place the pellet stove in your living room or use an insert in existing open fireplace. Propane is just as expensive as oil if not more so and follows oil prices. Pellets can be sourced more locally like Maine and gives you an alternative option to lean on if oil/propane shoots up in price.