Web upgrade doesn't complete -- next steps?

I attempted to upgrade my 0704 installation to 0710 via the web. Unfortunately, after several reboots during the process, my core has a bunch of empty files in /etc and other directories (making this particularly knotty, /etc/passwd is one of the empty files) and keeps trying to continue the failed upgrade each time I reboot it.

I'd like to get back to my functioning 0704 before re-attempting the upgrade from DVD this time. I think I can handle writing a find command to replace all the files with their *.pbackup versions, but how do I stop the incessant upgrade process given that I'm going to have to do all this from a live CD?

I also seem to have a corrupt mysql database, as I can no longer access the orbiter page via the admin web interface. Will this be solved by the upgrade, or is there an easy way to regenerate the proper table contents?

Also, when I do the upgrade, is it safe to leave my data drives attached, or is there a chance that these disks would be wiped out by the installer? What if I just do a new install of 0710 over my 0704?

That's a lot of questions, but I'm willing to work at this. Thanks!

Bret