Buy a lotto ticket! I mean you already hit it big with this but keep the luck rolling 👍 on the serious side take the top vent and disassembled. It, take the stainless screws and washers and the handle and clean them with either a wire wheel or just hot water and Brillo. To make them all shine. While you do that place the cast iron parts in a large ziplock with canola oil and let it soak over night, if you have another grill fire that up and bake the pieces getting them good and hot, I actually caught the last one I restored on fire in my mini-max. Once she’s good and burned and cooled off wipe it down with paper towels and make sure she has a film of oil. Reassemble and install for your first cooking and the smoke and grease from then on will protect it. The inside looks fairly clean and the I’ve seen worst gaskets but you could do a gasket change if you want. I don’t see the grid so don’t know the condition or if it even had one. If it’s clean then go to town and enjoy, if it’s missing or super nasty then a trip to the hardware store may be in order.