Short version: Are stores (food and climbing) open in Santiago (de Chile) on Sundays?

Long version: We are looking to fly into Santiago, quickly grab some supplies, and head out to Cajon del Maipo (by private car) the same day. We were hoping to arrive on a Saturday, but it turns out flights that arrive on Sunday are cheaper. Would it still be possible to find open stores (we would need food and fuel) on a Sunday?

Thanks!

Normal supermarket food shouldn't be a problem. Fuel. Gasoline is always available, but maybe you need gas canisters? Not sure if you can find that on a Sunday.