Please Help

Question

Yesterday my engine light went on in my 2002 Chrysler Sebring convertible.The car is running fine, I checked the oil at a gas station by an attendant who said the color was ok and it was 1/2 full. I am due for an oil change in a couple of months. I turned the ignition on and off for the codes and got P1684 and P0455. What are these codes, and what kind of a fix will they need, and how much will it cost to fix the problems? I am a single widowed mother of 2 small children, so am very anxious this is going to cost a fortune, of which I do not have. Thank you so much for any help, Sara.