fwiw, I used this howto and the one on f9 to f10 with preupgrade-cli to do a headless upgrade from f8 to f10.  I can strongly recommend trialling on a virtual machine before doing the upgrade.

I found that there's an issue somewhere in the upgrade chain with the nspr rpm, which can leave you with an upgraded machine on which very little works. A workaround is to extract the missing 4 libs from the f10 base repo's rpm (nspr-4.7.2-2.fc10.i386.rpm) using rpm2cpio and drop them into /lib after running preupgrade-cli, but before rebooting. Then update f10 once installed. I also had to re-enable sshd before the reboot, as the upgrade disabled it, leaving an upgraded headless box that cannot be logged into.

 hth

Tim