"Upgrade existing system"

[Mark]

Hi,

Can somebody tell me what exactly will happen when I "upgrade an existing system" to a new release?
In this particular case, it would be FC3 to FC5 or FC6.
Will it just upgrade to newer versions of currently installed RPMs, or will there be more complex changes?

How big is the risk of something going wrong during the upgrade and my system being (partially) broken - assuming that I have a
pretty "standard" server installation (text-mode only, no X11)?

Also, can I do a direct upgrade 3->5 or 6 or should I do 3->4->5->6?



Thanks,

MARK