Start with the o2 sensor. There are 2. The primary is on top the exhaust right next to the cat. A lot of times a faulty o2 sensor will throw other fuel related codes, so sometimes fixing the o2 will make the other codes go away.
It's extremely easy to change the o2. Just take out the old one, buy a new one from
www.oxygensensors.com and plug it back in. If you want the plug and play one it'll prob cost more. Save yourself some money and just splice the wires yourself.