No prob, this is why I'm here for.
Good luck with upgrade, and backup, or even better, clone your disk before going for upgrade. Borrow an external USB of sufficient size, and download Carbon Copy Cloner, let it do a full clone, once done go ahead with upgrade. If anything goes bad, just boot from clone, and make another clone but this time from external to internal disk, and you are back to where you were before the upgrade.
It is faaaaar less stressful then fixing the things, and still does not limit you to try to fix them but if you fail to succeed then you just boot, clone and you are safe.
Cheers
Zsolt