[support] Extra measures to take before upgrading?

Hello all.

Excuse in advance for the question, maybe too simple...

This will be my first upgrade after the security advice I received. I am on Drupal 7.0. I have read in detail the instructions and I have a full backup in my hard disk now (local) I will do the same wit5h the database in a few moments. I understand correctly what they say to do (I guess).

A couple of questions

1) It is no the same if I upload ALL the content of the upgrade without deleting all folders before?

2) Any extra advise you have for newbie people in Drupal before doing with the upgrade?

Thanks in advance.

Jorge Biquez