97 Nissan Maxima Codes P0446, P0325, P0440

My Check Engine Soon light came on yesterday and I took it to get the codes run and it came back with P0446, P0325, and P0440. I asked the service guy at Advance Auto what these meant and he didn't seem to know but suggested I check out some of the online forums. I am just wondering how important it is that I get these checked out/replaced ASAP. I am a student and really really short on cash and am trying to figure out if I can put this off for a little bit. I have read some of the other forums and don't really understand a lot of the technical jargon, but form what I gather these codes are pretty common in Nissans. I was just kind of hoping for some advice in layman terms. Thanks to anyone with advice

You have a malfunction/very small leak in the cars emissions system. (P0440, P0446).

The easiest/cheapest possible fix is to replace the gas cap with a new one from the dealer (Aftermarket caps are shakey at best).

The P0325 is a Knock Sensor or circuit.

Either the sensor has to be replaced (more likely, given the age of your vehicle) or the wiring has either a short/open circuit.

Both repairs won't set you back very much.

Good luck and keep us posted.