Help with Upgrade Instructions

I think because I’m so new to WP, there are things in the upgrade instructions themselves that I’m not sure I’m understanding. IF someone extremely kind and patient gets the time, and FEELS like helping, could that kind and patient someone please answer a few very specific questions I have about the upgrade instructions themselves? I have written out my specific questions below. They appear in bold near the original text of the upgrade instructions they refer to. Thanks in advance, whoever you are. ??

EXISTING INSTRUCTIONS:
5. On the server, delete the directories wp-admin and wp-includes. Note: If you have “languages” directory in your wp-includes folder (with .mo files) you may want to save/backup those before deleting the wp-includes directory. Upload the new ones. Does the phrase ‘upload the new ones’ refer to wp-admin and wp-includes, or to the .mo files?

6. The Classic and Default themes have been changed slightly so if you wish to, you can upload those to your wp-content folder. Does ‘if you wish to’ mean this entire step is optional and that if you choose NOT to do this part, your site will look just like it did before you started this upgrade process?

7. On the server and at blog root, delete the old WordPress files and upload new ones. I recommend you do this one by one if you are not sure. Do not delete wp-config.php.

Does ‘at blog root’ mean on the server, or on the local machine, or both?

Which “old WordPress files” specifically, are to be deleted? Everything in certain folders? If so, which certain folders?

“upload new ones” refers to which files/folders, specifically?

Is the wp-config.php file that we are NOT to delete on the server or on the local machine, or both?

Bonus Miscellaneous Question:
a) I think I know, but just to be certain, which of the following files, which I have modified since installing 1.5 a few weeks ago, would I need to MANUALLY go re-edit or re-install or ? AFTER doing this upgrade, in order to have my tweaks back as I had them BEFORE the upgrade:

wp-login.php
wp-admin/menu.php
wp-includes/functions.php
wp-includes/templates-function-category.php
styles.css (in default theme folder)
comments.php (in default theme folder)
index.php (in default theme folder)

THANKS for any help. ?? I truly hope this is clear. I’m sorry but I find the instructions a little murky. It’s just me, I know.