I only have these codes P0171 & P0174, I'm not sure what to replace

What is your question?

I thought oxygen Sensor, don't know if I replace top or bottom or both? Auto parts store gave me a list of about 20 things I needed to replace???? Can someone please help me?

What makes this problem better or worse?

I change the plugs & wires because diagnostic reader said 3 cylinder was misfiring, but a few months ago the same code P0171 came up

How long has your 1996 Ford Ranger had this problem?

About 2 months