If I understand correctly, /etc stores all my configuration files. If I backup the entire /etc directory to CD, then reformat, reinstall the same distro and restore an older version of /etc, will I regain all my customisations?

Will the difference in dates cause problems?
Will touching fix these?
Are there any other key areas I should back up, preserving-customisation-wise?
Are all the different variations of the Linux mascot (with sword, with shield, with wine, etc) the same Tux, or does he lead an empire?

Will the difference in dates cause problems?
No, the file will be overwritten because it is the same filename

Will touching fix these?
It will not be needed.

Are there any other key areas I should back up, preserving-customisation-wise?
/home and depending if you installed other packages and changed the location of the configuration file. I'm don't use knoppix or mandrake, but I've done with when I reloaded server before.

Are all the different variations of the Linux mascot (with sword, with shield, with wine, etc) the same Tux, or does he lead an empire?
Many people distort Tux to fit their distro, I prefer to leave the penguin as he is since he's never done anything to me(better yet, get a lizard).