1. How do I remove items on the Grub boot lornel and I want to remove the old item.
Removing a kernel with rpm -e should automatically remove the Grub entry. If you just want to remove the entry, you can edit /etc/grub.conf
2.) Is it possible to change the default selection in Grub? If so, how?
Sure, just add the line
to /etc/grub.conf where x is the number of the entry you want to be the default, starting at 0.
3.) Does anyone know if the SB Audigy sound card works under linux? I get an error when I try to open the mixer and there is no sound.
Don't know. Have you tried to run the sound configuration tool, /usr/sbin/sndconfig?
4.) If I don't plan on playing any games (I only use linux for programming), is it worth to install the latest nvidia video drivers? I'm asking that cos I don't have a clue how to install em and would rather not.
You only need the drivers if you want hardware acceleration for OpenGL or if you want to use XV for instance in video players.