I have the P0325 and P0440 codes coming from my 97 i30. 175,000 miles.

From what I have read, the Knock Sensor would not have made the light come on but the Evap System will and now that it has, I get both codes. I replaced my Oil Pan Gasket, Transmission Pan Gasket last weekend. Filled the tank and the next day the SES Light came on.
Today, the battery sounded dead in the morning. This afternoon it left me stranded and I had to get a jump. The alternator and battery are about 2 years old and were working great last week.
What could I have done to it during the process of replacing those two gaskets last weekend that has made all this happen? Also would either of those two codes make my battery drain itself while parked, or make something stay on while parked? Or is it all just bad luck and coincidence?

Any help is appreciated.

Also any links to diagrams or how-to's for the replacement of those two items would help a lot!

Have you tried replacing your gas cap? That's a very common cause for P0440 and other EVAP codes. Worth a try since it's cheap and simple.

Also, have you read this thread yet?
p0440-1997-maxima-t146134.html

I replaced the gas cap when I first had the codes pulled. I figured just in case.

The more pressing concern is the fact that I am dealing with a dead battery now, and finding out why it died. Liek I said the alternator and battery are both fairly new and it was fine a week ago. When I got a jump it ran all the way home no problem so I am thinking the Alternator is probably good, but what would have drained the battery is a mystery.

A good battery must read >12.5 VDC with engine off. A good alternator must have a charging voltage >13.8 VDC (spec is 14.1-14.7 VDC). The alternator voltage must be stable. A bad/weak battery poses a heavy load on the alternator. A failing alternator (internal diode or voltage regulator failure) can give all sorts of problems (like the ones you have). So make sure both the battery and alternator are in good condition. Also check the alternator and battery harness for any 'crossed wires.' Make sure you did not pinch any wire based on your last maintenance activities.

If the above are Ok, use an ammeter (clamp type or 'series' type) to measure battery current with engine off. Parasitic drain (from controllers, security system, etc) are usually <50uAmps (0.050 Amp). Anything more than that requires further investigation (disconnect fuses one at a time to isolate problem).

If all of the above are good, then you can tackle the fault codes directly.