Will, That was an excellent post and should be read by many just getting started. I couldn't agree more to avoid the auto shooting modes as much as possible and learn to shoot in manual first. The camera metering system is very good and taking the time to learn exposure levels, composing the shot ad understanding the basics is the best and IMO the only way to start. It well may be the only way much of the time. Like many "old schoolers" I learned on a K1000 and there was no other choice. Once you got familiar with how the shot would turn out at different exposures and settings you could produce better shots than anyone with a camera in auto.
An example? Try to shoot a decent sunset/sunrise in auto. The camera will almost always overexpose the shot and you loose a lot of the colour that is there.
As for excessive noise this camera should be very good up to ISO 800. So if this is happening at this or lower settings then there is something going on in camera unless that card added a lot of random data somehow. I would always suggest you shoot at the lowest setting possible if you can and my camera is always not higher than 400 unless the scene demands it.
He's a couple of great web sites that offer many very good tips for shooting, style and technique. I also agree with Will that a good book or 2 are indispensable.
The Online Photographer: Totally, Completely Okay: The Pentax K100D
The Radiant Vista
The Luminous Landscape
and the basics:
PENTAX digiich