Update Linux Kernel?

I am currenlty using RHN for updating my firewall, but always exclude the kernel packets because I am so green with Linux and am just listening to what the guy that set it up told me – which was that it would mess up the os to do kernel updates – to just upGrade. Meanwhile – at the rhn site, updating kernels are only a problem with older release dates and only when using up2date. Does anyone have any suggestions? I’m afraid to update the kernel, upGrade the version, and more afraid NOT to with all the security scares.