Editing page content through FTP?

I currently work with a graphic designer and code primarily HTML/CSS for clients looking to develop a web presence. I don’t know much about WordPress. I have a client who wants some minimal changes done to his site, simple things like removing one of the tabs, editing some text, changing some links. His site is hosted through GoDaddy and I’ve gotten FTP access to all the files. Once I got in, I discovered that his site was created using WordPress – but he has no knowledge of this at all. The previous developers set up everything for him.

So my problem is that I can’t login to the actual WordPress account (because our client doesn’t even know that it exists, so he doesn’t know the login) and I can’t find anywhere in the file structure where the actual content – what you see on the page – is created. There’s a lot of PHP files calling things like get_header(). My question is, where is that header information coming from? How do I find the actual HTML so I can edit it? Is there even a way to do this through FTP or do I have to be able to log in through WordPress?

I apologize for having such a beginner question. Thank you for any light you can shed on this for me.

If the content is dynamically written, you won’t be able to change this through ftp.
At the template files the content is called by typing <?php the_content(); ?>(or the_content(); ) if already scripting in php.

You need to get his WordPress login information to log in to his website, over there you can see pages, and the names of the pages, once in there it is really easy to edit.
The menu structure will mostly be found in appearence > menu (also in wordpress itself, not ftp)

if you see get_header(); it calls the file in that directory called header.php, same with sidebar etc..

Sometimes there is a little html in it, sometimes it is all dynamicly.