2002 Ford Taurus Error Code P0316/P0301?

So I just financed a used 2002 Ford Taurus in Denver Colorado. It's currently at 70,100 miles. It was an "as is" deal. No warranties.

Today my check engine light (flashing while driving) came on and I headed down to autzone to find out what it was. I got P0316/P0301 so obviously cylinder 1 is misfiring. The car also rumbles a ton when stopping or at a dead stop.

In terms of fixing it what could it be and about how much would it be?
In regards to the used car dealer, what can I do?

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