I'm running FC1 aswell, and this is my kernel version.
andrew@zeus incoming$ uname -sr
That's what you're running, I assume?
I didn't have any problems after upgrading to it, except a small problem with WINE. What problems are you experiencing?
As for your 2nd question, I believe all the security fixes in the lastest 2.4 kernel were backported to the RedHat/FC kernel, so upgrading to improve security isn't nescessary. You can upgrade if you want, but it's not absolutely nescessary.