I would try un-installing itunes and reinstall by following the instructions exactly that appear on the screen. I know personally I have used ipods/itunes for around 3 years and I have never had problems using either.
What exactly happens when you try to import MP3 to your ipod?
Is your Ipod new, if so it may need formatted (or similar) in order for itunes to recognise it?
Personally I always import music from cd and I have never done this directly from my computer to ipod although it should be possible to do this.