Will deleteing all themes make go to default?

I installed a new theme and got “If this file were writable you could edit it.” So I came here and searched. I followed the directions to change permissions to 666 by right clicking wp_content (wI think I was supposte do the theme??)

Now my blog is gone. I can’t get it at all.

To correct I think I made it worse.

I was trying out several new themes. And I could not remember which it was set to so I set permissions on several. Now I think I made it worse. I have no idea what permissions I should be using.

Can I go in through Dreamweaver, delete all themes but default and get back my posts?

If not how do I get back my posts?

THanks