Hi Mr. Risbert,
The address you gave (gdiblog.brady2014.ws) would be fine to place in the Learning Bonus area. That will show that you completed that step.
As far as editing the posts:
Yes, you can absolutely edit the posts. It's very easy to do in your WordPress Admin Area. Just click on Posts -> All Posts -> Then under the post you want to edit click the Edit button. When you are done editing either click update (to publish your changes) or click preview (to see your changes and decide if you want to keep them) or click save draft to save your changes until later.
As far as header:
You can absolutely change what it says. You'll need to spend some time getting to know your WordPress admin area.
However, every theme is a little different as far as headers, footers and so on.
I would advise that first, again, you get to know your admin area. Second, visit the GDI tutorials in your GDI members area. Some great help there.
Also, do a Google search on how to WordPress and you will find some great help out there. Videos and articles and so on.
So, yes, you can make major changes to your blog. And it's really easy. It will just take you a little time to learn all the ends and outs.
Always remember, a blog is not written in stone. You can change the way it looks, edit posts and pages, erase them or add more. Never wait for perfection. It will probably never be perfect in your eyes. Action is the key. The rest will come with time and knowledge.
Hope this helped a little.
Good luck and I'll leave a comment on your blog to say hi.
Have fun!
Vince