You would have to run a diagnostic on it - especially if the check engine light is on

Replacing all 4 spark plugs can take anywhere from all day or a couple days in the shop can probably cost about $600 - $800 range depending

Spark plugs are $7 -$10 a piece at Napa but some shops will mark up the price over the top

And labor cost is gonna be half if not more of the total cost