What would it cost to have the fuel gauge and check engine light repaired by you

What is your question?

I have a 2002 Isuzu Rodeo S, that has the same problem like others the gas gauge not working right and the check engine light on. The vehicle was just purchased by me at a used car lot that wasn't very honest but the vehicle does have only 60k miles on it. If professionals or repair pal fixed this problem what would it cost me? It's a 4cyl.