I agree. Do a complete backup of your site and database. I personally had quite a few changes in core files due to mods. I did have a record or what mods I installed so that was easy to reinstall. For me, the easiest thing to do was to build a new site (using a test area) and duplicate it. It didnt take that long and I know probably not as easy as HL's, but I chose to have those mods, so its my responsibility.

You wanna see what I did, I wrote it here:
http://www.boonex.com/unity/forums/topic/My-7-0-1-Upgrade-Experience.htm

Dont see more be scared. This is how you learn... Just make sure you have your backups in place :).. Oh yeah.. have a drink for me too :)