Help Please!

I've got a 2000 jetta 2.0 and the check engine light had been on for a while and never really checked it. When I had it checked, there was 8 codes, ranging from on output from o2 sensor, to air to fuel mixture wrong, to lean mixture, and to 3 different cylinder misfires. Keep in mind, these had been accruing for like a year. So I had the o2 sensor replaced two days ago, and it has been running like a champ, better gas milage and no light. My car didn't run as poorly as you said, just some hesitation, lack of power, and poor gas milage, so it might be more than that for you. But if you do have to get an o2 sensor. Get it from NAPA or napaonline. Com. I looked everywhere for o2 sensors, and they wanted around $100, in not more. I got mine for $44, same EXACT part as the others who wanted $100 like autozone, advance auto, vip, etc. Bosch, and it wasn't universal, it had the connector and everything. Saved myself $50 easy there, so check there first, i've noticed lots of times their parts are cheaper.