1999 Kia Sportage Check engine light codes

Ok heres what your codes mean:
P0131-#1 oxygen sensor, low voltage
P0171- system to lean (not enough gas in the mixture)
P0326- knock sensor
P0453-evaporative control system pressure sensor, high imput
yes its going to be exspensive if you bring it in somewhere, if you fix it yourself, its still going to be a little pricey. As you stated you are 60, so if I were you id try to bring the car back to where you got it. You have 3 days after the purches to "re-nigg"(unless they changed that) if you got it from a dealer id raise hell till they fixed it for free. Other wise id look for a new car if I was you. Hope it helps