P0441 diagnostic code (O2 sensor problem)

Just bought a used '99 Corolla yesterday and i get an "engine check" light today.
So i went to Autozone and had them do a free diagnosis and they came up with this:

P0441: The PCM has determined that the purge flow in the evaporative emission control system is incorrect for the current engine operating conditions.

The autozone guy said that this was an O2 sensor problem and that there are 2 sensors .. one before (150$) and one after (70$) the catalytic converter. It seems i have to buy the 150$ one.

considering that i just bought the car paying a hefty sum, my question is ... how critical is this problem? What are the consequences if i don't fix it??
i have 37000 miles on the car and don't know anything about cars by the way. This is my 1st car too.

thanks in advance.

autozone is pretty good at pulling codes, but most parts guys have no clue as to what the codes mean

The ECM records PO441 when evaporative emissions leak from the components or when there is a malfunction in either the VSV for EVAP, the VSV for vapor pressure sensor or in the vapor pressure sensor itself.

DTC Detecting Conditions:
- The pressure in the charcoal canister does not drop during the purge control (2 trip detection logic)
- During purge cut-off, the pressure in the charcoal canister is very low compared with atmospheric pressure.

Trouble Areas:
- Open or short in VSV circuit for EVAP
- Open or short in VSV circuit for vapor pressure sensor
- Open or short in vapor pressure sensor circuit
- VSV for EVAP
- VSV for vapor pressure sensor
- Vapor pressure sensor
- Vacuum hose cracks, hole blocked, damaged or disconnected
- Charcoal canister is cracked, holed or damaged

>>> Check the items in red first.

(VSV is vacuum switching valve)

This is more than likely a problem with one of the control solenoids in the evaporative system. It has nothing to do with the oxygen sensors. We've been seeing more newer toyotas with this type of problem. Mostly camrys. I would get it checked at a shop that knows what theyre doin.

Thanks all for the responses.
So some place like midas would be able to fix it?
I am pretty sure a toyota dealership will want 100 bucks just to look at it :(
Also anybody knows if its a serious problem like my engine crapping out or fuel efficiency getting affected?
I understand that from the list someone suggested .. it can be due to several reasons.
But is this anything that i should freak out about?

Thanks

no tire stores, go to a good independant shop