Well, I took out a pushrod or two today because I though one might be bent. Turns out they aren't, but when I was looking at them, at least a couple of them had some surface rust/pitting/corrosion. Is this bad? What is this a sign of? What should I do?

 

you got moisture/water into your motor... I'm guessing intake manifold gasket failure?
They're cheap enough to replace. How bad are they? If a stock motor with stock valve springs, then it'd probably take a fair bit of corrosion before they're weak enough to fail.

 

Could also be a sign of a faulty PCV system.